Up to 20 people were presumed dead off Russian-annexed Crimea after a fire engulfed two fuel ships, authorities said on Tuesday.
The blaze broke out when one vessel was transferring fuel to the other on Monday, driving both crews to jump into the icy waters of the Black Sea.
Russian authorities rescued 12 people and recovered 10 bodies, Alexei Kravchenko, spokesman for Russia's Federal Agency for Maritime and River Transport, told AFP.
The other 10 people were missing and most likely dead, he said.
"There is no hope of finding them alive," Kravchenko said. "It is no longer a rescue operation."
Three of those missing sank into the water "before rescue workers' eyes" without life jackets, he said.
Kravchenko added that as of Tuesday morning the fire was continuing. "There's an endless amount of fuel there," he said.
The ships, the Candy -- also known as the Venice -- and the Maestro, had crews from India and Turkey and were both sailing under the Tanzanian flag.
The Candy had a 17-strong crew, while the Maestro carried 15.
- Flashpoint area -
Both vessels appear on a list of ships that are at risk of being targeted by US sanctions over petroleum shipments to Syria between 2016 and 2018.
Ukraine's government said that at the time of the accident AIS tracking devices had been turned off on both vessels.
It claimed that Russia encourages vessels to turn off tracking devices in order to hide from Ukrainian authorities and blamed Moscow for the accident.
"This time, an accident led to horrible consequences -- people's deaths," said Ukraine's ministry for temporarily occupied territories and internally displaced persons.
It said it was hard to establish the origin of the gas transported by the vessels but that the ships were used to transport gas from Ukraine and other countries.
India said it was in touch with the Russian authorities.
"Our embassy in Moscow is in constant touch with the concerned Russian agencies to get more information on Indian nationals affected in the incident and to extend necessary assistance," the foreign ministry said.
The accident occurred outside Russia's territorial waters and close to the Kerch Strait, a flashpoint in tensions between Russia and Ukraine.
In November, Russia fired on and seized three Ukrainian navy vessels in the Kerch Strait as they tried to pass from the Black Sea to the Azov Sea.
The confrontation was the first open military clash between Kiev and Moscow since 2014, when Russia annexed Crimea and a pro-Russian insurgency erupted in eastern Ukraine.