The raid on the UK-owned 32,000-dwt OceanCenturion (built 1999) took place on Tuesday, 45 miles from Lome, Togo, a security source told Reuters.
The ship was looted, but the two hostages were later released.
Speedboats were used to reach the tanker,which is operated by Union Maritime of London. The company is not commenting.
The tanker has been escorted into Lome bylocal naval vessels.
The IMB confirmed an attack on a tanker in the region, saying cash and personal belongings were taken.
A Geden tanker was hijacked off Gabon onMonday, with 24 crew on board.
