Last week, about 1 million barrels of Sokol crude from Russia’s Far East were delivered to an Indian refinery.

Half of that volume was loaded after two ship-to-ship transfers, one of which involved a US-sanctioned tanker, data from Kpler and Vortexa Ltd show.

Other US-sanctioned vessels have transferred cargoes of Sokol that are due to be delivered next month, according to Kpler.

Oil traders closely monitor purchases by India, which became the biggest importer of Russian seaborne barrels after Moscow’s invasion of Ukraine, as well as US-led efforts to frustrate those flows.

The western-led curbs, which were reinforced in January, are broadly designed both to keep oil flowing to avoid a vicious price spike, yet also restrict the benefits for Moscow.

India has previously said US-sanctioned vessels won’t be allowed to discharge their cargoes in the country, although Prime Minister Narendra Modi’s government has also maintained it abides only by UN restrictions, and doesn’t follow curbs imposed by any individual country or a bloc.

The oil ministry didn’t reply to an email seeking comment for this story.

“There will always be an element of calculated risk in Indian imports of Russian crude, but the refiners have mostly played it safe,” said Vandana Hari, founder of Vanda Insights in Singapore.

“Essentially, they can’t be held accountable for how the crude is transported,” Hari said.

In late March, Viktor Titov, an Aframax that was sanctioned by the US treasury department in January as part of a broad wave of curbs, picked up about 500,000 barrels of Sokol from Russia’s De-Kastri terminal, data show.

After sailing toward Nakhodka Bay near Russia’s Kozmino, Viktor Titov performed a ship-to-ship transfer with Night Glory a week later.

That vessel, an Aframax, then sailed to the waters off Malaysia, where it transfered the cargo to a Suezmax, Cordelia Moon, which discharged at the Jamnagar refinery in west India in late May.

The Night Glory and Cordelia Moon are both sanctioned by the UK, but not by the US.

Reliance Industries Ltd, which owns the Jamnagar refinery, didn’t reply to an email seeking comment.

Calls made to the UAE-based owner of Viktor Titov, and the China-based owner of Night Glory didn’t go through.

The safety manager of Cordelia Moon didn’t respond to an email.

Other US-sanctioned tankers have also been involved in the trade, including Captain Kostichev and Victor Konetsky, Kpler data show.

Captain Kostichev loaded 699,000 barrels of Sokol from Sakhalin 1 in late April, then transferred it to Monte 1, which is expected to discharge at Jamnagar in early June.

Victor Konetsky did a ship-to-ship transfer to Night Glory in Nakhodka Bay in mid-May. Tankers may switch destinations.

Owners of Captain Kostichev and Victor Konetsky, which share the same contact details as Viktor Titov’s owner, didn’t answer calls seeking comment. Emails to the owner of Monte 1 were unanswered.

India became Russia’s main seaborne crude market following the 2022 invasion of Ukraine as Western buyers shunned the flows.

Imports are set to hit a record 2.196 million barrels a day this month, as new tankers joined the trade following the wave of US sanctions that were announced in January.

“At this moment, the US does not seem to be tightening enforcement or ramping up its Russia oil sanctions,” said Hari.

“If and when that changes, you will probably see the refiners retreat for a while, play it safe. They have now become adept at riding these waves,” Hari added.