Nigeria ? Kidnappers seized a woman from the Philippines on Wednesday in Nigeria’s oil-producing region, police said, marking the first female captive known taken in an upsurge of violence roiling Africa’s oil giant.

Attackers in the southern oil city of Port Harcourt abducted the woman as she got of her car, Rivers state Police Commissioner Felix Ogbaudu said.

Meanwhile, a British oil worker taken hostage last month was freed Wednesday because he fell ill, officials said.

The Briton was abducted along with an American in a Jan. 23 raid by unknown assailants in Port Harcourt. There was no immediate word on the American’s fate.

A year of intensified violence in the Niger Delta, where all of the crude in Africa’s biggest oil producer is pumped, has cut daily output by nearly a quarter, helping send global oil prices toward new heights.

Militants and criminal groups have bombed oil installations and kidnapped more than 100 foreigners in the region.

Militant groups say they are fighting to force the federal government to give their region a greater share in oil wealth. Despite the region’s enormous oil deposits, most of its people are poor.