The captain of a Laskaridis reefer is among those taken hostage by Nigerian pirates.
The 335,938-cbf Saronic Breeze (built 1991) was hijacked last week off Benin, before being taken to Nigeria and then released after the master, a second mechanic and a cook were abducted by the gunmen.
All three are Russians, according to the Russian embassy in Lagos.
Embassy spokesman Artyom Romanov told the Tass news agency: "The parties concerned are exerting all necessary efforts for their quick release."
There were 18 Russians and two Ukrainians on board at the time of the incident.
