Gunmen attacked a barge belonging to an oil services company off the coast of Nigeria on Saturday, killing two Nigerian sailors and kidnapping four foreigners, navy officials said.

The suspected sea pirates stormed the vessel in the Gulf of Guinea, an area that has seen a sharp spike in the number of reported marine attacks over the last six months.

A spokeswoman for Sea Trucks Group, which provides support vessels to oil companies operating in Nigeria, told AFP that one of the company’s ships came under fire and that four of the firm’s employees were taken in the raid.

“At this time Sea Trucks Group is making every effort to ascertain the whereabouts of its personnel,” the spokeswoman, Corrie van Kessel, told AFP.

She said that Sea Trucks Group is heavily involved in the oil and gas sector in the Niger Delta.

Nigeria’s navy spokesman Commodore Kabir Aliyu said during the attack “four expatriates are reported to have been kidnapped from the vessel; two sailors were killed.”

He said those kidnapped were from Indonesia, Iran, Malaysia and Thailand.