India has warned its seafarers and commercial vessels face heightened security risks while operating in the “highly volatile” area around the Black Sea, saying the number of drone and missile attacks by both Russia and Ukraine on ships in the region is rising.

Indian nationals working on commercial vessels have been asked to “carefully assess” the situation while operating or transiting through the conflict-affected region in the Black Sea, the Indian foreign ministry said on Sunday.

At least five Indians are among 11 people killed in attacks on commercial vessels in the Black Sea since April as Russia has stepped up attacks on the cargo ships in the Black Sea maritime corridor.

Russia and Ukraine have both ramped up strikes on ships in the Black Sea and the Azov Sea. Ukraine claims that it is targeting Russia’s so-called shadow fleet – ships that transport oil in violation of international sanctions.

The Indian foreign ministry said it had observed an “increase in the number of such incidents on commercial vessels” and said those who undertake such journeys should exercise the utmost caution.

“Indian nationals intending to undertake employment on commercial vessels operating in or transiting the conflict-affected region are advised to carefully assess the prevailing security risks before accepting such assignments,” the ministry said in a statement.

It asked seafarers to obtain comprehensive information from employers and ship operators regarding the vessel’s route, port of call and security arrangements while remaining in contact with family members.

Seafarers should ensure that the terms of employment comply with applicable international maritime standards and provide adequate provisions for medical care, evacuation, repatriation, and compensation in the event of an emergency.

Three merchant vessels with Indian crew members on board have come under attack within just a week in the Black Sea amid Russia’s war on Ukraine.

In the latest attack on Saturday, two Indian crew members went missing after MV AGN Ragnar, a Palau-flagged cargo ship, was attacked by three drones. The remaining seven crew members, including two Indians, were safely evacuated by the Ukrainian coast guard.

The Indian Embassy in Kyiv said a search and rescue operation has been launched for the two missing seamen. The two, identified as Chandra Ram Dubey and Deepak Kumar Gupta, reportedly jumped into the sea when the vessel was attacked.

Earlier, a vessel identified as the MV Omorfi was struck in Russian territorial waters, killing an Indian crew member. There were 10 crew members on board in total, including three Indian nationals.

The Forward Seamen’s Union of India (FSUI) said the deceased was chief officer Sagar Gupta and said he was killed in a “Ukrainian drone attack” while on board the Omorfi at Novorossiysk.

It came a day after four Indian seafarers were among 10 crew members killed in multiple strikes on bulk carrier MV Golden Leo, which was carrying 17 crew members. One Indian crew member was critically injured in the Russian strike.

India strongly condemned the strikes and summoned a Russian diplomat following the attack on the Golden Leo. The attack was the deadliest of its kind on a commercial vessel in the Black Sea since the war began.

But Russia refused to apologise for the attack, saying it will not stop targeting shipping to and from Ukraine. The Kremlin alleged that the vessel in question was “transporting ammunition” or other military goods, without providing evidence.

Indian seafarers – more than 300,000 are employed globally – have increasingly been caught up in the wars between Iran and the US as well as Russia and Ukraine.

Manoj Yadav, general secretary of the FSUI, said at least 17 Indian seafarers have been killed in the two conflicts. He claimed the actual death toll could be higher and described the situation as a serious human rights concern.

“The continued attacks on Indian nationals, whether by the US, Iran, Russia or Ukraine, show that international law has been put at stake,” he said.

Mr Yadav alleged that the families of the deceased seafarers had received neither compensation from the Indian government nor adequate recognition for their loss. He also warned that the risks to Indian seafarers were growing as tensions spread to the Red Sea, where Houthi attacks continue to threaten commercial shipping.

“Why is the Indian government silent?” he asked.