LAGOS--Gunmen kidnapped 12 foreign sailors after attacking a cargo ship in the waters off the coast of Nigeria's oil-rich Niger Delta region, a Nigerian navy officer said Saturday.

"The attack took place some time last evening and only one ship was involved.... One of the crew members was injured from gunshots and 12 were taken hostage," navy spokesman David Nabaida told AFP.

Nabaida said information he has is that the attacked vessel, the BBC Polonia, is German-flagged, but according to the MarineTraffic.com website, it is an Antigua Barbuda registered ship which was heading to Nigeria's Onne port, situated on the Bonny estuary, close to the oil hub of Port Harcourt.

The navy managed to board the vessel and sailed it to safety at Bonny anchorage, Nabaida said.

The crew member who was injured in the attack is Ukrainian and is in a stable condition at a hospital in Bonny, he added.

Nabaida identified the seized crew as seven Russians, two Germans, one Lithuanian, a Latvian and another Ukrainian.

The Baltic state of Lithuania confirmed from Vilnius one of its nationals was among the snatched seafarers.

"Information about an abduction from a German vessel off the Nigerian coast, including one Lithuanian sailor, was received from German authorities and the circumstances are currently being checked," a foreign ministry spokesman told AFP.

No group has yet claimed responsibility for the attack.

Thousands of militants who for three years waged a so-called oil war in the restive Niger Delta have been getting restless following months of delays in their post-amnesty retraining exercise.

Some have complained of poor reward after they surrendered arms, warning that they might return to the creeks to fight if the situation does not improve.

Around 20,000 former militants who were fighting for a fairer share of oil revenues to go to local communities, laid down their arms under an amnesty deal in the oil-rich region between August and October last year.

Under the deal, the government promised to provide cash, amenities in the region, jobs and retrain the ex-combatants.

Local media reports on Saturday said a top government official directing the post-amnesty project was last week roughed up by a group of former fighters who were due to start the retraining and rehabilitation exercise in southern Cross River state.

Violence by armed rebels in the region between 2006 to 2009 played havoc with oil output, which dropped in this OPEC member state to around a million barrels per day as against 2.6 million barrels at peak production level.

Hundreds of people, both locals and foreigners, most but not all of them linked to the oil sector, have been kidnapped in the restive Niger Delta in recent years.

Most have been released after a few days or a few weeks in captivity, very often after the payment of a ransom.