Rival ethnic militant groups have fought for a third consecutive day in Nigeria's oil rich Niger Delta region, as authorities try to cope with what they are calling a "very serious situation."
Witnesses and police officials spoke of heavy gunfire and street battles Sunday in Warri, the capital of southeastern Delta State, between ethnic Ijaw and Itsekiri militants.
There are no casualties figures for Sunday's clashes. But authorities imposed a curfew in Warri after at least three people died during violence Friday and Saturday. Some reports put the death toll as high as 20. At least 30 homes were destroyed in the fighting.
Fighting between the Ijaw and Itsekiri has claimed hundreds of lives in recent years and disrupted oil production, which is vital to Nigeria's economy.
The origin of the latest clashes is not yet clear, but competition for the region's oil wealth is often a trigger for violence.
In addition to the ethnic tensions, residents in the Niger Delta region say they do not get a fair share of the area's oil profits. They regularly vandalize pipelines to siphon off fuel, sometimes setting off deadly fires.
Nigeria is the world's sixth largest oil-producing nation.