Nigeria ? A previously unknown Nigerian militant group claimed responsibility Friday for kidnapping four foreign oil workers and blowing up a pipeline – dual attacks that cut Nigeria’s oil output by 10 percent.

Gunmen on Wednesday stormed an offshore oil platform run by Royal Dutch Shell in the volatile Niger Delta and seized the workers – an American, a Briton, a Bulgarian and a Honduran.

In a phone call to The Associated Press in Lagos, a man who identified himself as Brutus Etikpaden said his group carried out the kidnapping and an attack on an oil pipeline early Thursday.

In an attempt to prove his group was holding the hostages, Etikpaden passed the phone to two of the men he said his group had abducted – one identified himself as American, the other as British.

Earlier, the head of Nigeria’s navy, Vice Adm. Ganiyu Adekeye, told reporters in the southern oil port city of Warri that security forces had located a boat carrying the gunmen in the waterways of the oil-rich Niger Delta. He said an attempt would be made soon to rescue the captives.