An oil tanker capable of carrying 2 million barrels has 'exploded' off the coast of Nigeria, according to reports.

The Trinity Spirit - an oil production ship operated by 10 crew members - reportedly exploded at the Ukpokiti oil field near the Escravos terminal close to the River Niger delta.

It is not clear just how much oil has been spilled - though the incident marks Nigeria's second environmental disaster in three months.

Videos show huge clouds of black smoke rising into the air as the Trinity Spirit sinks.

There are "no reported fatalities" at the time of writing.

The Trinity Spirit is a type of ship used by the offshore oil and gas industry for the production and processing and storage of oil.

These models have a similar function to larger oil rigs.

Ikemefuna Okafor, CEO at Shebah Exploration and Production Company Limited, told Reuters: "At this time there are no reported fatalities, but we can confirm that there were ten crew men on board the vessel prior to the incident and we are prioritising investigations with respect to their safety and security."

The incident comes as an oil slick off the coast of Thailand continues to expand towards beaches on the east coast, home to fragile coral and seagrass.

The leak occurred on Tuesday evening at a mooring station about 20 kilometres south east of the Map Ta Phut Industrial Estate, south of Bangkok, Star Petroleum Refining said.

The oil leak from an undersea hose at an offshore mooring point used to load tankers was stopped early on Wednesday, January 26 - but not before 140 to 375 barrels, or between about 22,000 and 60,000 litres, spilled into the Gulf of Thailand.

“Cleaning up the oil slicks in the sea may take five to seven days, but if the oil slicks reach the shore, it will take years to rehabilitate the environment,” Thon Thamrongnawasawat, a prominent Thai marine biologist, told the Associated Press.

“So we have to do everything possible not to let it hit the shore,” he said.