Image (c) Michael Kamber

The Nigerian military has made six arrests after four soldiers and a policeman were killed in an attack by suspected pirates in the oil-rich Niger Delta on Friday.

Security forces also recovered a cache of arms and ammunition in the raid on their camp, the army said.

Gunmen in four speed boats targeted the military checkpoint in southern Bayelsa state on Friday, authorities said.

Piracy and organised crime linked to oil theft are common in the region.

Image (c) AFP