South Korean tanker explosion kills 5.

France-Presse - A South Korean fuel tanker sank Sunday after an explosion on board, leaving five crew members dead and six missing, the coastguard said.

The 4,191-tonne ship carrying 11 South Koreans and five Myanmar citizens sank near Jawol island, about 32 kilometres off the western port of Incheon where the vessel had unloaded its cargo, a coastguard spokesman told AFP.

Yonhap news agency reported that the explosion was likely caused by gases leaking from the ship's oil tanks, citing an official from the firm that owns the vessel.

"We believe that something went wrong during the process to take out remaining gas in the oil tank," the Doora Shipping official told the agency.

"The vessel usually transports diesel, but this time it carried gasoline. We are now examining whether it had any relation to the explosion."

The dead crew members included one South Korean, two Myanmar citizens and two others whose nationalities have not been identified yet after their bodies were recovered later from the sea.

The two unidentified victims were among five South Koreans and three Myanmar crew who had been earlier reported missing, said the spokesman, adding an emergency operation involving dozens of patrol ships was ongoing.

Five others were rescued earlier.

Authorities were still investigating the cause of the explosion, which happened in the Yellow Sea, but the coastguard said it was unlikely to be the result of any hostile action by North Korea.

"The explosion took place far below the sea border with North Korea. We see very little possibility (of attacks by the North)," the spokesman told AFP.

The flashpoint maritime border with the North on the Yellow Sea was the scene of deadly naval clashes in 1999, 2002 and 2009.

Seoul accused Pyongyang of torpedoing one of its warships with the loss of 46 lives in March 2010. The North denied involvement but went on to shell a border island that left four South Koreans dead in November 2010.