Royal Dutch Shell says a fire has broken out at one of its oil wells in southern Nigeria.

Shell says firefighters are battling the blaze on a wellhead in the Cawthorne Channel, south of the city of Port Harcourt.

The company says it had to close a flow station, cutting production by almost 38,000 barrels a day.

A spokesman for the oil giant says the cause of the fire is unknown.

The blaze comes one day after a local militant group, the Movement for the Emancipation of the Niger Delta threatened to renew attacks against oil installations in the region.

The group said the Nigerian military used a Shell airstrip to launch a helicopter attack. The military said it attacked barges used by oil smugglers, while the militants said the attack targeted ethnic Ijaw communities.

Militant attacks forced Shell to close other flow stations last month.

Some information for this report was provided by AFP and Reuters.