Pirates have stormed an US-flagged oil supply vessel off southern Nigeria and kidnapped the ship's American captain and chief engineer.
A C-Retriever owned by American oil servicing company Edison Chouest Offshore was attacked on Wednesday off the city of Brass, said AKE, a London headquartered private security firm.
"Both the chief engineer and the captain were kidnapped," Richard Fylon of AKE said.
"They are both American."
US defence officials in Washington, who requested anonymity, confirmed the details.
An official at AKE's Lagos office told AFP this was the first reported kidnapping of US nationals around the oil-producing Niger Delta region in at least two years.
The official, who requested anonymity, said the same area was attacked by pirates earlier this week, but that there appeared to have been no increase in naval patrols operating in the area.
Security forces in the Niger Delta and the Nigerian navy did not answer calls seeking comment.
Oil servicing ships have been struck repeatedly in recent months around the Gulf of Guinea, which includes the waters off Nigeria, Togo, Benin and parts of Ghana.
Sailors of varying nationalities have been taken hostage, but typically released days or weeks later.
Most analysts say ransoms are paid in such cases, but the companies involved and Nigerian officials rarely comment on payments to kidnappers.
