Automatic weapons fire punctuated by screams erupted after dark yesterday in a Nigerian city located near villages where massacres just two days ago left more than 200 people dead.

Nerves remained on edge, despite a long-standing dusk-till-dawn curfew in Jos, the capital of Plateau state. When sustained gunfire rang out for about three minutes, apparently from several automatic rifles, people ran screaming through the streets.

More than 100 people, mostly women and children, sought shelter in a hotel where journalists and military commanders were staying. They wailed in terror as they heard gunshots coming one by one from outside. A ranking police officer in Jos said the shooting happened after people gathered in the street because of a suspicious truck in their neighbourhood.

The officer, who spoke on condition of anonymity, said soldiers opened fire to scare away the group.

However, human rights groups say extrajudicial killings remain common in Nigeria -- especially in situations of civil unrest.

Evarisitus Fuanbal, a former soldier who now works at Jos's City Lodge Hotel, said the military officers staying at the hotel left last night after receiving word of people assembling nearby.

Earlier yesterday, the U.S. government and human rights activists called for Nigeria to investigate and prosecute those responsible for Sunday's killings.

Acting President Goodluck Jonathan had promised the fighting would stop after more than 300 people, mostly Muslims, were slain in January. Some described Sunday's massacres, which targeted Christians, as revenge for what happened in January. Others said the bloodshed has ethnic roots, with Fulani cattlemen wanting to take over nearby land.

Human Rights Watch urged Jonathan to provide protection for villages surrounding Jos, a central Nigerian city that has become the epicenter of violence in the region.

Jonathan fired his national security adviser Monday following the weekend violence.

"After the January killings, the villages should have been properly protected," UN high commissioner for human rights Navi Pillay said. "Clearly, previous efforts to tackle the underlying causes have been inadequate, and in the meantime the wounds have festered and grown deeper."

Those who survived attacks Sunday in three mostly Christian villages said security forces never provided them any guards.

Human Rights Watch researcher Corinne Dufka said authorities must protect the communities, bring the perpetrators to justice and address the root causes of violence.

The U.S. Embassy in Abuja, Nigeria's capital, called on Nigeria's federal government to seek justice "under the rule of law and in a transparent manner," the embassy said.