Six vessels carrying almost 5 million barrels of Russian oil failed to reach their destinations in India, some idling kilometers off the coast for weeks without providing a reason, Bloomberg reported on Dec. 20.

Recent U.S. sanctions targeting the violators of the $60-per-barrel price cap could partially be the reason, the news outlet speculated.

The U.S. Treasury Department sanctioned the NS Century ship, belonging to the Russian Sovcomflot shipping company, on Nov. 16 for violating the price cap.

Two days later, the vessel halted south of Sri Lanka while carrying Russian oil to the Indian port of Vadinar.

In the past week, NS Century was later reportedly joined by two other Sovcomflot-owned tankers carrying oil to Vadinar.

Two more tankers heading to another Indian port, Paradip, also came to a sudden stop before reaching their destinations, and another ship may soon join them, according to Bloomberg.

Five of the listed vessels belong to Sovcomflot.

Both the U.S. and the EU began ramping up sanctions to enforce the price cap on Russian seaborne crude. The measure was imposed last year to limit Moscow's oil revenue without destabilizing global markets.

Although Russia managed to largely avoid the cap in recent months by using a fleet of uninsured "ghost" tankers, Russian oil and gas profits dropped by 41% in 2023 amid tightening sanctions.

With the West weaning itself off Russian oil, Moscow turned to new markets like China and India, offering discount prices.

India is an especially important customer for Russia, as it has been buying more than 60% of Russia's seaborne oil, making it the second buyer of Russian seaborne crude after China.