Nigerian army frees hostages

By Segun Owen

WARRI, Nigeria (Reuters) - Nigerian security forces said on Saturday they rescued 13 hostages kidnapped this week, including nine foreigners, and destroyed a key militant camp in the heart of Africa's biggest oil industry region.

Nigeria's main militant group has declared an "all-out war" and warned oil companies to evacuate their staff in the Niger Delta following three days of heavy clashes with the military.

The army said its forces, using navy gunboats and helicopters, would continue an offensive to flush militants out of the creeks after the hijacking of two oil vessels and attacks on troops in southern Delta state.

Global crude oil markets have largely ignored the clashes in the OPEC member country, closing lower in two of the last three sessions.

"We will carry on with our operations until we stabilise the situation," said Colonel Rabe Abubakar, spokesman for the military taskforce in the Niger Delta, adding two soldiers were wounded in this week's fighting.

Royal Dutch Shell, U.S. oil major Chevron and other energy companies working in the area were given until Saturday by the militants to remove their workers.

Security sources have said they are taking the militant threats seriously but there are no plans to evacuate more staff.

The military on Friday freed nine Filipinos and four Nigerians that were kidnapped two days earlier when their oil vessel MV Spirit was hijacked by militants near Warri in Delta state, Abubakar said.