(Reuters) – Lloyd’s Register has told India's Gatik Ship Management, which has become a major carrier of Russian oil since the Ukraine war, that it will withdraw certification of 21 of its vessels by June 3, the maritime services company told Reuters.

It is the latest setback for Gatik, which was also been forced to find new flags for 36 of its ships after they were deflagged by the St. Kitts & Nevis International Ship Registry.

“Lloyd’s Register is committed to facilitating compliance with sanctions regulations on the trading of Russian oil,” it said in an email to Reuters. “Where supported by evidence, we withdraw class and services from any vessels found by the relevant authorities to be breaching international sanctions.”

Classification societies such as Lloyd’s Register in London provide services including seaworthiness checks, certification that is vital for securing insurance and entry to ports.

Lloyd’s Register said, however, that 11 of the Gatik vessels it was declassifying were also certified by the Indian Register of Shipping.

Gatik, which is based in the Indian city of Mumbai according to shipping databases, did not respond to emailed requests for comment.

A major U.S. insurer, the American Club, also told Reuters it was no longer providing cover for Gatik ships, while Russian insurer Ingosstrakh said it would not work with Gatik in future.

Neither the insurers, Lloyd's Register nor the flag registry spelled out exactly why they have dropped business with Gatik.

In response to Russia's invasion of Ukraine, Western powers imposed a price cap on Russian crude of $60 a barrel.

While non-EU countries can import seaborne Russian crude, Western shipowners and insurers are prohibited from handling such cargoes unless they are sold at or below that price.

Last month, spot prices for Russian crude rose above $60 a barrel and some ship insurance executives said they were nervous of falling foul of the rules as they were unable to independently track the value of cargoes.

India does not recognize the sanctions imposed on Russia and has quickly become the biggest buyer of seaborne Russian crude.

Western efforts to curtail the amount of revenue Russia earns from its energy resources are having a disruptive impact, as are Western sanctions on oil exports from other countries such as Iran and Venezuela.

But the opacity and limited oversight of the shipping sector means many vessels with cargoes from countries targeted by sanctions continue to sail by finding new flags and non-Western registries or insurers, raising concerns about safety and liability.

Every ship requires documents including a flag registry.

Ships typically have protection and indemnity insurance which covers liability claims including environmental damage and injury. Separate hull and machinery policies cover vessels against physical damage.

While Lloyd's Register is dropping classification for 21 Gatik ships, at least 28 were listed as certified by the Indian Register of Shipping, according to the IRClass website.

IRClass, which is recognized globally, did not respond to requests for comment.

Gatik emerged this year as a leading carrier of Russian oil to India using a fleet of tankers that has numbered more than 40, shipping data shows.

The American Club, one of the world’s top 12 P&I insurers which combined provide cover for about 90% of the world’s ocean-going tonnage, said it previously covered most Gatik ships but as of early April was no longer covering them, declining to say why.

Ingosstrakh, a large Russian insurer active in ship coverage but not part of the top 12, told Reuters this month that its insurance cover for Gatik’s Prometheus tanker expired in April and had not been renewed.

Ingosstrakh said it “had to decline certain requests for insurance it received from Gatik due to the risks identified as part of our adverse media screening procedure,” citing negative media coverage without being more specific.

“We can also confirm that we do not plan to work with Gatik in the future,” the privately owned Russian insurer said in response to queries from Reuters.