Lagos, Nigeria (CNN) -- Gunmen attacked a barge belonging to an oil service company near the coast of Nigeria on Saturday, killing two sailors and taking four foreigners hostage.
The remaining four sailors were taken to a nearby hospital where they were treated for injuries, according to Navy spokesman Commodore Kabir Aliyu.
"The Nigerian Navy ... dispatched a naval ship and helicopter to protect and secure the area," said Aliyu.
It is not clear who was responsible for the attack or how many foreigners were on board. Their nationalities were not immediately known.
Africa's most populous nation is a top oil supplier though has been mired in ethnic and religious violence, which in recent years has been compounded by an Islamist insurgency.