Armed raiders have attacked two product tankers off Nigeria, the IMB said.
The two separate incidents took place near Lagos on 7 January.
In one raid, two men boarded a tanker at anchor and tried to steal cargo.
They were halted by duty crew who raised the alarm.
The raiders escaped without taking anything.
In the second incident, up to five attackers in a skiff tried to board another ship, but turned away after the alarm was again raised.
The tanker had also managed to send a distress signal to the Nigerian navy.
