SEOUL (AFP) - The pirates who kidnapped three South Korean sailors have been identified as Nigerians, according to Yonhap news agency.

The 500-tonne Marine 711, with about 40 Ghanaian and three South Korean sailors, was boarded by unidentified pirates last Monday (March 26).

The pirates seized the three South Koreans and escaped on a separate speedboat, with their current whereabouts unknown.

The Marine 711, registered in Ghana, later arrived at a port at Ghana where the Ghanaian sailors disembarked, according to Yonhap.

The South Korean government has deployed anti-piracy warship Munmu the Great to the sea off Ghana.

Munmu the Great had previously been involved in anti-piracy operations in the Gulf of Aden.

"We are closely coordinating with local countries including Ghana, Nigeria, Togo and Benin as well as the US and the EU to locate our nationals and secure their release," South Korea's Foreign Ministry said.

The pirates have not yet demanded a ransom in return for the release of the abducted sailors.