A Russian tanker carrying thousands of tonnes of oil products broke apart during a heavy storm on Sunday and spilled oil into the Kerch Strait, while another tanker was also in danger after sustaining damage, Russian officials said.

The ships were in the Kerch Strait between mainland Russia and Crimea, which Russia annexed from Ukraine in 2014, when they issued distress signals.

Russian investigators opened two criminal cases to investigate possible safety violations after at least one person died when the 136-meter Volgoneft 212 tanker, with 15 people on board, split in half with its bow collapsed.

State media footage showed waves lapping at its deck.

The Russian-flagged ship, built in 1969, was damaged and had run aground, officials said.

An unverified video posted on Telegram showed some blackened water in stormy seas and a half-submerged tanker.

The second Russian-flagged vessel, the 132-meter Volgoneft 239, was adrift after sustaining damage, the Emergency Situations Ministry said. It has a crew of 14 and was built in 1973.

Key route for fuel exports, grain

The Kerch Strait is a key route for Russian grain exports and is also used for exports of crude oil, fuel oil and liquefied natural gas.

In September, Ukraine accused Russia in an international court of violating the law of the sea by trying to keep the Kerch Strait under its sole control, which Moscow rejects as unfounded.

Emergency services said one person had died, but 12 other people had been evacuated from the first tanker. Eleven of them were taken to hospital, with two in serious condition, the TASS news agency said, citing Alexei Kuznetsov, assistant to the health minister.

The Ministry of Emergency Situations said it was still in contact with the other tanker and its crew after the vessel ran aground 80 meters offshore near the port of Taman at the southern end of the strait from Kerch.

Each of the tankers has a cargo capacity of around 4,200 tonnes of oil products.

Official statements did not provide details on the extent of the spill or why one of the tankers was so badly damaged.

President Vladimir Putin ordered the government to create a task force to deal with the rescue operation and mitigate the impact of the fuel spill, Kremlin spokesman Dmitry Peskov was quoted as saying by news agencies, after Putin met with the ministers of emergencies and the environment.

Russia said more than 50 people and equipment, including Mi-8 helicopters and rescue tugs, had been deployed to the area.

Svetlana Radionova, head of Russia's natural resources watchdog Rosprirodnadzor, said specialists were assessing damage at the site of the incident.