SEOUL, March 31 (Xinhua) -- Three South Koreans were presumed to have been kidnapped by pirates in seas off Ghana, the foreign ministry said Saturday.

Marine 711, a fishing boat with three South Koreans aboard, was believed to have been abducted in seas off Ghana at about 5:30 p.m. on Monday (Ghana time), according to a press release from the foreign ministry.

While the abductors had been driving the fishing boat to the waters off Nigeria, three South Koreans were taken away on a separate speed boat. The whereabouts of the speed boat and the abductees were not known yet.

South Korea's Joint Chiefs off Staff (JCS) said the abductees, which were reportedly known to have been a captain, a mate and an engineer, had been kidnapped by Nigerian pirates.

The remaining 40 sailors of Ghanaian nationality were reportedly set free. The fishing boat arrived at a Ghana port on Wednesday.

A South Korean battleship, which was operating in the Gulf of Aden, was dispatched early Wednesday to the nearby sea, the foreign ministry said.

The South Korean government is closely cooperating with Ghana, Nigeria and other nations to find out the whereabouts of the abducted people.