JOS: Nigeria's government sent in troops to the flashpoint Jos region on Monday after machete-wielding gangs attacked Christian villages, killing at least 500 people, officials say.

Police arrested scores of people in the wake of the attacks which came just weeks after another outburst of Muslim-Christian violence, which left hundreds dead.

Newspapers said Muslim residents of the villages had been warned by phone text message to escape two days before the attacks.

Witnesses meanwhile described how the victims of Sunday's three-hour orgy of violence, mainly women and children, were caught in animal traps and fishing nets as they tried to flee their attackers, who hacked them to death.

The official death toll was initially put at a little over 100 but Dan Manjang, an advisor to the Plateau state government, said it had shot up.

"We have been able to make 95 arrests but at the same time over 500 people have been killed in this heinous act," Dan Manjang told AFP.

Government-run radio also reported that 500 people had been slaughtered in a raid on three villages on the fringes of Jos, capital of Plateau state.

Witnesses and local rights activists put the figure at between 200 and 250.

Much of the violence was centred around the village of Dogo Nahawa where gangs from the mainly Muslim Fulani ethnic group set fire to straw-thatched mud huts before embarking on the killing rampage in the early hours of Sunday.

Frank Tatgun, a resident of Dogo Nahawa, said that he had seen two armoured vehicles and three military trucks arrive in the village and scores of troops were now on patrol.

The explosion of violence is the latest between rival ethic and religious groups in the region. In January, 326 people died in clashes in Jos, according to police although rights activists put the overall toll at more than 550.

A curfew which was imposed after January's unrest is supposed to be still in place but Christian leaders said the authorities had done nothing to prevent the bloodshed.

"Shortly after the militants beseiged Dogo Nahawa ...we contacted the soldiers at exactly 1:30am. But we were shocked to find out that the soldiers did not react until about 3:30am after the attackers had finished their job and left," Plateau State Christian Elders Consulatative Forum (PSCEF) said in a statement.

"The attack is yet another jihad and provocation," said it added.

Witnesses said armed gangs had scared the victims out of their homes by firing into the air but most of the killings were as a result of machete attacks.

Survivors said the attackers were able to separate the Fulanis from the Beroms by chanting 'nage', the Fulani word for cattle. Those who failed to respond in the same language were hacked to death. One local paper said the gangs chanted "Allah Akhbar" -- Arabic for "Allah is the greatest", before breaking into homes.

Other residents said the few Muslims in the villages received SMS messages warning them to leave the area before the attack.

Many of the victims in Sunday's attacks were hacked to death as they tried to flee into woodland.

Rights activists said the attack appeared to be in revenge for the January clashe in which mostly Muslims were killed.

"I think it's a reprisal from the Fulanis for the earlier attacks," said activist Shehu Sani.

Locals said the attacks were the result of a spiralling feud between the Fulani and the rival Berom clan which started out with the theft of cattle, then worsened after a deadly revenge attack.

The office of Acting President Goodluck Jonathan said the security services in Plateau and neighbouring states had been placed on red alert to ensure the violence did not spread.