Abuja - Rioting in two southern Nigerian cities Thursday over a police killing forced Muslims to take shelter at barracks over fears they would be targeted in reprisal attacks.

The riots broke out in Onitsha and Asaba after a police officer shot dead a bus driver, police said. Both cities are mainly populated by Igbos, who are overwhelmingly Christian.

Hausas, who are mostly Muslim and often originate from Nigeria's north, took shelter at police and army barracks, though there were conflicting reports over whether any were attacked.

Attacks blamed on Islamist group Boko Haram, some of which have targeted Christians, have sparked fears of reprisals and have led Christian leaders to warn they would defend themselves if the violence continued.

"A police corporal accidentally shot a bus driver dead in Onitsha and this angered the people, who went on the rampage in protests, and the situation caused fear among Hausa residents,"

Anambra state police spokesman Emeka Chukwuemeka told AFP.

He confirmed that Hausa residents had fled to police and army barracks, but added that none had been attacked following the protests.

Chukwuemeka could not say how many fled, but added that the policeman had been arrested.