Street clashes between rival ethnic gangs in the southwestern Nigerian oil city of Warri have left several people dead.
Political tension is mounting as Africa's most populous nation of more than 120 million people heads for presidential elections in April, the first poll to be supervised by civilian authorities in more than 20 years.
Residents said between four and eight people, including a soldier, died in fighting between Itsekiri and Urhobo youths on Friday. Many others were injured, while about 10 houses were torched.
Residents said the street battles may have been sparked by the rerun of regional primaries for the ruling Peoples' Democratic Party held on Friday in the Niger Delta area.
The Itsekiri and Urhobo have been at each others' throats since the 1990s when a dispute over the site of a local government headquarters ended in the killing of over 100 people.
Nigeria is facing its worst cycle of violence since the late 1960s, when civil war erupted over the breakaway republic of Biafra. More than 10,000 people have died in political, communal and religious clashes since more than 15 years of brutal army rule ended in 1999.