JOS, Nigeria - New gunfire rocked Nigeria's troubled city of Jos, sending residents fleeing to police barracks for shelter, and troops patrolled mainly Christian areas on Wednesday.

Tensions remained high amid accusations that military chiefs ignored warnings about a massacre in which more than 500 people were killed with machetes and guns in Christian villages on Sunday.

Residents packed police barracks after an eruption of gunfire on Tuesday night but most returned to their homes early Wednesday.

Speaking from her house in Bukka Uku, a resident said soldiers fired into the air to disperse crowds of mainly Christian youths who gathered after the arrest of a Muslim Fulani man in the neighbourhood.

"Because of the tension and anxiety in the area, we took it for a gunfight and left our homes for the police barracks," Josephine Emmanuel, a Bukka Uku, resident told AFP.

Residents said soldiers remained on the streets of Jos, where thousands have died in ethnic strife in recent years and which lies on the dividing line between Nigeria's mainly Muslim north and Christian dominated south.

Jonah Jang, governor of Plateau state, said security lapses had worsened the massacre carnage.

Jang told reporters he had alerted Nigeria's army commander about reports of movement around the area and had been told that troops would be heading there.

"Three hours or so later, I was woken by a call that they (armed gangs) have started burning the village and people were being hacked to death.

"I tried to locate the commanders, I couldn’t get any of them on the telephone."

Officials said more than 500 people from the mainly Christian Berom ethnic group were hacked to death with machetes, axes and daggers in the villages of Dogo Nahawa, Ratsat and Zot on Sunday morning.

Troops patrolled the three villages but residents of neighbouring villages said they had received new threats.

Some survivors told of the attacks as they recovered. In a surgical ward of Jos hospital, women with deep scalp wounds mourned the loss of their children.

Chindum Yakubu, a 30-year-old mother of four, described the screams of her 18-month-old daughter who was plucked from her back and hacked to death as the family tried to flee the pre-dawn attacks.

"They removed the baby and killed her with the machete," Yakubu said.

There are growing fears about ethnic tensions in and around Jos.

"One moment it's relaxed, then the next moment people are running for their dear life," said hospital administrator Ruth Mutfwang, summing up life in the restive region.

International observers have called on the government to take action over the tensions.

The UN's human rights chief Navi Pillay said, "what is most needed is a concerted effort to tackle the underlying causes of the repeated outbreaks of ethnic and religious violence... namely discrimination, poverty and disputes over land."

Nigeria's senate described the attacks as acts of "terrorism" and crimes against humanity.

But the main opposition Action Congress accused the government of "hypocrisy," saying perpetrators of the violence in recent years had not been brought to justice.

Archbishop John Olorunfemi Onaiyekan of Abuja has objected to descriptions of a conflict between Christians and Muslims.

"This is a classic conflict between herdsmen and farmers, only the Fulani are all Muslims and the Berom all Christians," he told Vatican Radio.

"The international media are quickly led to report that it is Christians and Muslims who are killing one another; but this is not true, because the killings are not caused by religion but by social, economic, tribal and cultural issues."

Sunday's attacks were only the latest between rival ethnic and religious groups. Locals said they resulted from a feud first ignited by cattle theft that was fuelled by deadly reprisals.