Russia's defence ministry said on Sunday its air defence systems had shot down four Ukrainian military aircraft over the past 24 hours, just two days after Ukrainian President Volodymyr Zelenskiy said Kyiv had downed three Russian fighter-bomber jets.

In its daily dispatch, the defence ministry said its air defence shot down three Su-27 fighter aircraft and one Su-24 tactical bomber in the Zaporizhzhia and Dnipropetrovsk regions of southeastern Ukraine.

The dispatch provided no further details.

On Friday, Zelenskiy said the country's forces shot down three Russian Su-34 fighter-bomber aircraft on the southern front, hailing it as a success in the 22-month-old conflict.

The commander of Ukraine's air force also said the planes had been downed.

Reuters was not immediately able to corroborate the battlefield reports from either side.

Ukraine's Air Force claims to shoot down 3 Russian Su-34 fighters

Ukraine claimed its Air Force shot down three Russian Su-34 fighter bombers on Friday amid a surge in attacks in the southern Kherson region.

 Ukraine's military leaders claimed Saturday they have shot down three Russian fighter jets on the southern front, marking a first in the 22-month-old war between the countries.

The trio of Su-34 fighter bombers were brought down over Kherson region on Friday, the Ukrainian military General Staff announced in a social media update.

"Over the past day, the Defense Forces Aviation has struck 12 areas of concentration, weapons and military equipment of enemy. Also, the air defense destroyed 3 Su-34 fighter bomber," they said.

Ukrainian President Volodymir Zelensky acknowledged the downed aircraft in his nightly address on Friday.

"Grateful to our soldiers who destroyed three Russian Sukhoi aircraft at once in the South, in our Kherson region," he said. "It's the gain of our Air Force and the direct action of the Odessa Anti-Aircraft Missile Brigade. Thank you, guys! And may every Russian pilot be well aware of our response to every Russian killer -- none of them will go unpunished."

Official Russian media did not mention the downing of the aircraft on Saturday, but Russian bloggers writing on the Telegram messaging app acknowledged the loss, Sky News reported, adding that analysts told Ukrainian television U.S.-supplied Patriot missiles had probably been used.

The claims came as Russian forces stepped up their attacks on the southern Kherson region over the weekend.

Ukrainian presidential office deputy chief Oleksiy Kuleba said Saturday in a Facebook post there have been almost 500 attacks in the area with more than 2,500 shells fired since the beginning of this week.

"This is an average of one hundred attacks per day," he wrote, adding that two people were killed and another 28 wounded in the Kherson region.

"We are strengthening sky protection in every region of Ukraine," Kuleba said. "Most Russian drones today [were shot down by] mobile fire groups. Their work is effective and helps to save missiles to destroy enemy winged missiles and aviation."

Ukraine's air force said on Friday it had shot down three Russian Sukhoi Su-34 fighter-bombers in the south of the country, with President Volodymyr Zelenskyy stating it had happened in the Kherson region where fighting continues to rage.

"At noon today, three Russian Su-34 fighter-bombers were shot down in the southern operational zone," the commander of the Ukrainian Air Force, Mykola Oleshchuk, announced on Telegram.

In his speech on Friday evening, Zelenskyy specified that these jets had been shot down by missiles, and said he was "grateful to our soldiers who destroyed three Russian Sukhoi aircraft at once. In the south — in our Kherson region".

"Let every Russian pilot know about our response to every Russian killer — none of them will go unpunished", Zelenskyy added.

The Air Force did not say what happened to the pilots of the planes.

Authorities in Moscow did not immediately confirm the incident. However, the oft-cited Russian military blog Fighterbomber referred to "combat losses" caused, in their view, by the US-supplied Patriot anti-aircraft defence system.

What are Su-34s and why does this strike matter?

Su-34 is Russia's most advanced twin-seat supersonic medium-range fighter-bomber — a type of jet not commonly found in western arsenals, with the US-made F-111 and F-15E Strike Eagle being the most similar multirole counterparts.

In service since 2014, Moscow deployed the jet on missions in Syria and Ukraine. Despite the Kremlin touting it as the crown jewel of its military aviation, Su-34s have been used in low-altitude bombing attacks due to a lack of guided missiles, exposing them to heavy air defences.

Since the beginning of Russia's full-scale invasion of Ukraine in February 2022, Moscow has confirmed the loss of at least 10 Su-34s in fighting with the Kyiv forces, while the actual number of downed jets is believed to be significantly higher.

Ukraine's Friday accomplishment is even more noteworthy considering that Russian forces have not lost more than one Su-34 on the same day since 5 March of last year.

Back in Russia, Su-34s have also been involved in several crash incidents, most notably on 17 October 2022, when one of the jets crashed into a residential apartment complex during a training flight in the city of Yeysk. At least 15 people were killed and 19 were treated in hospital, according to the local authorities.

In related news, the Dutch government announced Friday it is preparing to give 18 F-16 fighter jets to Ukraine, in a boost for the country's air combat capabilities.

The donation is believed to be a big step toward helping Ukraine gain significant ground in the fight for air supremacy — a powerful element of modern warfare Russia has used to its advantage to maintain its stranglehold on one-fifth of Ukrainian territory.