Sporadic shooting rang out overnight in the central Nigerian city of Jos and witnesses said at least one person was killed by soldiers enforcing a curfew days after attacks on three nearby Christian villages.
Jos, which lies at the crossroads of Nigeria's Muslim north and Christian south, has been tense since raiders attacked the villages of Dogo Nahawa, Zot and Ratsat just south of the city on Sunday, violence in which hundreds are feared to have died.
Fierce competition for control of fertile farmlands between Christian and animist indigenous groups and Muslim settlers from the north have repeatedly triggered unrest over the past decade.
Retaliatory attacks are not uncommon and Acting President Goodluck Jonathan has put the security forces on red alert to try to prevent unrest from spreading to neighboring states at the heart of Africa's most populous nation.
Last night until this morning everybody kept vigil. Nobody slept, said Felvis Aduba, a Jos resident who owns a shop selling electronic goods.
Jos was already under a dusk-to-dawn curfew after clashes between Christian and Muslim mobs in January which killed more than 400 people, according to community leaders.
Aduba said the city had been put on edge by SMS messages sent to mobile phones warning that militants from the Muslim Hausa-Fulani ethnic group, blamed for Sunday's attacks, were coming from the northern city of Maiduguri to wage war.
Gangs of youths gathered in self-defense, witnesses said.
Gunfire also rang out from the Tudun Wada neighborhood of the city overnight, where residents said panic was sown when a resident from another state received a truckload of cows.
Many of the herders around Jos are Hausa-Fulani and when a vigilante group saw the animals, they took the man for a northern Muslim and mobbed him, before the security forces opened fire to disperse them, killing one person.
POPE SENDS CONDOLENCES
The latest unrest at the heart of the oil-producing nation comes at a turbulent time, with Acting President Jonathan trying to assert his authority while ailing leader Umaru Yar'Adua remains too sick to govern.
The United Nations, United States, rights groups and opposition politicians have all urged the authorities to ensure those responsible face justice and called on the security forces to protect civilians.
My deepest condolences to the victims of the atrocious violence which has bloodied Nigeria and which has not even spared defenseless babies, Pope Benedict said in Rome.
Once again, with a sorrowful heart, I repeat that violence does not solve conflicts but only worsens their tragic consequences ... I call all those in the country who have civil or religious authority to work for the security and peaceful coexistence of the whole population, he said.
Plateau State Governor Jonah Jang on Tuesday blamed the military, which took control of security in January, for failing to respond to his warning that movements of armed men had been reported by villagers shortly before Sunday's attacks.
Police have made 93 arrests but rights groups are concerned that those responsible may not actually be prosecuted.
More than 300 people were arrested in January and about half of them were due to be sent to the capital Abuja for prosecution, but it is unclear how many actually faced justice.
Local officials said many of those responsible for January's violence were the same people arrested but not prosecuted after similar unrest in November 2008.