China and the Philippines' intensifying blame game over twin collisions in the disputed South China Sea is heightening the risks of armed conflict that could draw in the US, a Chinese observer has warned.

This comes as both sides dial up the accusations over the two incidents on Sunday involving coastguard boats from either side.

Chinese foreign ministry spokeswoman Mao Ning on Monday accused the Philippines of provocation "by repeatedly intruding into the Renai Jiao and continuing to spread disinformation".

Renai Jiao is the Chinese name for the Second Thomas Shoal - called Ayungin Shoal by the Philippines - an area in the South China Sea where the collisions took place. It is part of the Spratly Islands, known as the Nansha Islands in Chinese and claimed by both countries.

The incidents could represent a tipping point for ties between Beijing and the United States' oldest ally in Asia, warned Ding Duo, an associate research fellow at the National Institute for South China Sea Studies.

The Philippine defence minister earlier accused the Chinese coastguard of having "harassed and intentionally hit" its resupply ship and a Philippine Coast Guard vessel.

"We are here to really decry in the strongest possible terms this egregious violation and illegal act within the [Philippines'] 200 nautical mile (370km) exclusive economic zone and the obfuscation of the truth by China's distorting the story to fit its own ends," Gilbert Teodoro said in Manila on Monday.

While China has dismissed the encounter as a "slight collision", Philippine Coast Guard Commodore Jay Tarriela said on Monday that the damage to the resupply ship amounted to "more than a scratch".

The Philippines summoned the Chinese ambassador on Monday to lodge a diplomatic protest, while Beijing's embassy in Manila also said it had filed a similar complaint.

Sunday's face-offs came just ahead of the latest round of negotiations regarding a code of conduct in the South China Sea, where Beijing and Manila are among rival claimants. The talks, which started on Monday in Beijing, are aimed at preventing major armed conflicts in the South China Sea.

Beijing claims "indisputable sovereignty" over the Second Thomas Shoal, which has become the latest flashpoint in the resource-rich waterway, with frequent run-ins between Chinese and Philippine boats in recent months.

China has repeatedly blocked the Philippines from resupplying construction materials to the shoal, where Manila has kept a rusty World War II-era ship since 1999 to stake its claims to the waters.

No injuries were reported in the collisions on Sunday, but it was the first time in recent years that physical clashes had taken place, putting the dispute under the spotlight.

Two civilian supply boats are seen anchored at the derelict navy vessel Sierra Madre in this undated photo released by the Philippines Department of National Defence (DND) in November 2021. Beijing has tried repeatedly to block supplies to the ship, which is used by Manila to stake a claim on the Second Thomas Shoal. Photo: DND / AFP alt=Two civilian supply boats are seen anchored at the derelict navy vessel Sierra Madre in this undated photo released by the Philippines Department of National Defence (DND) in November 2021. Beijing has tried repeatedly to block supplies to the ship, which is used by Manila to stake a claim on the Second Thomas Shoal. Photo: DND / AFP>

Ding at the South China Sea studies institute, in China's southern Hainan province, warned of the impact on bilateral ties.

"Over the past years, the two sides have managed to control their differences well, so there is an unspoken agreement on how to deal with the disputes at sea," he said. "But now, such agreements have been broken."

Ding said the face-off could damage bilateral trust and affect the ongoing and long-awaited code of conduct talks.

"There would be less frankness in the negotiations."

The South China Sea is a busy trade route crucial to countries in Southeast and East Asia, and an escalation there would raise the risks of drawing in the United States, a treaty ally of the Philippines for more than 70 years.

Under their 1951 Mutual Defence Treaty, the US is obliged to defend the Philippines if its forces, ships and aircraft come under armed attack, including "those of its coastguard - anywhere in the South China Sea".

The commitment was reaffirmed in a statement released by the US State Department after the collisions on Sunday.

The same day, the US also conducted its first-ever trilateral aerial exercise with Japan and South Korea, in response to evolving North Korean nuclear threats.

However, "it remains to be seen how much the US would like to see a conflict between China and the Philippines to go out of control", Ding said.

According to Philippine officials, about five Chinese coastguard ships, eight accompanying vessels and two navy ships formed a blockade on Sunday to prevent two Philippine coastguard ships and two boats from delivering food and other supplies to forces stationed at Second Thomas Shoal.

A Chinese militia vessel, top, is seen near the Philippine coast guard vessel BRP Cabra as they approach the Second Thomas Shoal on Sunday. Photo: Armed Forces of the Philippines via AP alt=A Chinese militia vessel, top, is seen near the Philippine coast guard vessel BRP Cabra as they approach the Second Thomas Shoal on Sunday. Photo: Armed Forces of the Philippines via AP>

While coastguard vessels of both sides were involved in the incident, no direct conflict had taken place between them. It was a sign that both sides had sought to avoid the crisis spiralling out of control, Ding said.

But the risk of conflict remained high, he added, as the Philippines has said it will continue its resupply missions, and Beijing will not back down.

In an unusual move, China issued a quick statement after Sunday's first encounter. And soon after the second collision took place, it released two videos, purportedly taken from a coastguard vessel and a drone.

The Philippines, meanwhile, brought along a group of journalists on a coastguard ship, in an apparent attempt to put public pressure on China.

"This is a test for both sides," Ding said.

China and Philippines accuse each other over collisions in disputed South China Sea.

China and the Philippines on Sunday accused each other of causing collisions in a disputed area of the South China Sea, the latest in a string of maritime confrontations between the two countries that have heightened regional tensions.

In a statement, Philippine authorities said a Chinese Coast Guard ship carried out “dangerous blocking maneuvers” that caused it to collide with a Philippine vessel carrying supplies to troops stationed in Ayungin Shoal, also known as Second Thomas Shoal, in the Spratly Islands chain.

China’s move was “provocative, irresponsible and illegal” and “imperiled the safety of the crew” of the Philippine boats, the National Task Force for the West Philippine Sea said.

In a second incident Sunday, the Philippine task force said a Chinese maritime militia vessel collided with a Philippine Coast Guard ship, which was on the same mission to resupply the BRP Sierra Madre. Manila grounded the navy transport ship on Second Thomas Shoal in 1999 and has manned it with Filipino marines to enforce its claims to the area.

On Monday, Manila summoned China’s ambassador to the Philippines and filed a diplomatic protest against Beijing.

“China as a major power bears a heavier responsibility of contributing to peace and stability in the region,” said a spokesperson for the Philippine Department of Foreign Affairs.

Beijing claims “indisputable sovereignty” over almost all of the 1.3 million square miles of the South China Sea, as well as most of the islands and sandbars within it, including many features that are hundreds of miles away from China’s mainland.

In 2016, an international tribunal in The Hague ruled in favor of the Philippines in a landmark maritime dispute, which concluded that China has no legal basis to claim historic rights to the bulk of the South China Sea.

Beijing has ignored the ruling.

In a statement Sunday, the Chinese Coast Guard accused the Philippines of violating international marine law and threatening the navigation safety of Chinese ships.

It accused the first Philippine ship of trespassing into the waters of what it calls the Nansha islands and Renai Reef, prompting the Chinese Coast Guard ship to intercept “in accordance with the law,” and resulting in a “minor collision.”

In the second incident, the Chinese Coast Guard said the Philippine Coast Guard vessel “purposely provoked trouble and reversed course,” causing a collision with a Chinese fishing boat.

No injuries were reported in either collision Sunday, which marks the latest in a series of recent flashpoints between Beijing and Manila in the disputed waterway.

In September, the Philippine Coast Guard released video of a Filipino diver cutting a Chinese-installed floating barrier in a disputed area of the waterway that had prevented Filipino boats from entering.

It came just days after after the Philippine Coast Guard accused China’s maritime militia of turning vast patches of coral near the Palawan island chain into a bleached and broken wasteland.

China’s foreign ministry dismissed those allegations as “false and groundless.”

South China Sea: Why the Philippines and China are on a collision course.

Take a close look at a video of Sunday's "collision" between a Philippine coastguard ship and a Chinese maritime militia vessel in the South China Sea.

As the stern of one bumps the deck of the other, right in the middle of the frame is a Filipino television crew scrambling to get what in the business is called an "action piece to camera".

The confrontation between Manila and Beijing over submerged shoals in the South China Sea has been going on for decades.

But in recent months something has changed. The spats at sea are now unfolding in the full glare of the television media. This is the second time in weeks Philippine journalists have filmed a close encounter near a particularly sensitive reef known variously as Second Thomas Shoal, Ayungin Shoal or Ren Ai Reef.

This is no accident. It is part of a deliberate policy by the Philippine government to shine a spotlight on what it has called China's "brute force" in asserting control over what Manila says are its waters.

"I think we've seen a significant change this year. It's what I call an assertive transparency campaign," says retired Colonel Raymond Powell of Stanford University's Gordian Knot Centre.

Starting in January, the Philippine government began feeding more video of the encounters to local media. By summer it was taking more and more journalists, including the BBC, aboard its boats and aircraft heading out into the disputed waters.

"It's been like turning on a light to show China's grey zone operations," Col Powell says.

China appears to have been taken aback by these new tactics.

For a while it looked like the strategy was working, says Oriana Skylar Mastro of the Freeman Spogli Institute for International Studies: "We saw a bit of a lull in China's activities."

Beijing eased off and Manila was able to make several re-supply runs to an outpost it has on Second Thomas Shoal - an aged World War II-era landing ship called the Sierra Madre.

It was deliberately grounded on the reef in 1999. Since then, a tiny contingent of Philippine marines has kept lonely watch aboard the rusting hulk as it has gradually begun to fall apart. In 2014 a BBC team went aboard the ship. Even then it was in terrible condition with huge holes in its sides, and waves splashing through the structure.

 

Most analysts believe China has been content to play the long game. When relations between Beijing and Manila have been good China's coastguard has allowed resupplies to the Sierra Madre to go ahead. When relations have turned sour, they have moved to block the resupply ships.

But Beijing's overall assessment is that the Sierra Madre cannot last forever, and at some point, the Philippines will be forced to evacuate the marines, as the ship crumbles into the sea.

During the six years under former president Rodrigo Duterte that assumption appeared well-founded. But since the election of President Ferdinand Marcos Jr last year, the Philippines' foreign policy has turned 180 degrees.

Not only has President Marcos reversed Mr Duterte's policy of cosying up to Beijing, he has fully re-embraced the alliance with the United States and begun shouting loudly about China's incursions into Manila's 200-nautical mile Exclusive Economic Zone.

There's more. Sources in Manila say food and water is not the only thing the Philippines has been taking out to the Sierra Madre on resupply runs. They say it has quietly been shipping construction materials, including cement and scaffolding. The aim: to shore up the rusting ship.

"It's very hard to see how they could extend the life of the ship," Col Powell says. "I think we're coming to a crisis point. The end is near for the Sierra Madre. It could break up very soon."

Perhaps it is this new sense of urgency that is pushing both Manila and Beijing to greater assertiveness. The Philippines is desperate to cling to its presence on Ayungen Shoal. And Beijing is once again reiterating its power, determined that the Sierra Madre will not survive.

But if the Sierra Madre does finally crumble into the aquamarine waters of the South China Sea - or West Philippine Sea as its called in Manila - what happens then?

Will Beijing swoop in and attempt to seize control of the reef as it has done elsewhere in the South China Sea? Will Manila attempt to ground another vessel on Ayungin Shoal? And how will Washington react?

No-one knows but that day is coming, perhaps quite soon.