JUBA, Sudan, - At least 177 people have been killed in weekend attacks on villages of the Lou Nuer tribe by armed men from the rival Murle ethnic group in south Sudan's Jonglei state, a government official told Reuters on Monday.

By 4 p.m. yesterday, 177 dead bodies had already been found by our team, the commissioner of Akobo county, Doyak Chol, said. We are expecting more than 300 by the time all the places have been checked.

A spokesman for the south Sudanese army, Malaak Ayuen Ajok, said it had not yet been able to verify the number of dead but that it will not be less than 60.

A vicious cycle of cattle raiding and counter-attacks in southern Sudan has plagued the oil-rich region since Sudan's 2005 north-south peace deal ended one of Africa's longest conflicts but left southern civilians heavily armed.

The remote and marshy Jonglei state -- where French oil giant Total (TOTF.PA) holds a massive, mainly unexplored concession -- has been hit especially hard by cattle raiding and related killings that have fractured communities along ethnic lines.

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International analysts and officials in the southern government have worried aloud that, as well as disrupting peace, these clashes maintain a divisive atmosphere ahead of planned national elections in 2010 and a referendum on independence for the south in 2011.

In March at least 453 people, mainly women and children, were killed in Lou Nuer attacks on Murle villages, widely understood to have been in retaliation for the theft of 20,000 Lou cattle in January. A large number of cows were also stolen in that attack.

This time they targeted human beings, not cattle, Chol said, referring to this weekend's violence which he said was conducted by about 500 armed men. They were shooting indiscriminately. It was revenge.

He did not say how many of the dead were Lou Nuer and how many from the Murle attackers but said the unarmed Lou villages put up little resistance.

In one of the 16 razed villages, many children had drowned in a river as they tried to flee gunmen, Chol said. The attacks began before dawn on Saturday, he added.

The United Nations Mission in Sudan's (UNMIS) regional coordinator for the south, David Gressly, told Reuters that a U.N. team will travel on Tuesday to the hard-to-reach area to assess security and humanitarian needs following the violence.

A smaller, initial assessment team was sent on Sunday, he added, but was not able to verify the death toll.

A report on the March attacks by a joint team of different U.N. agencies, seen by Reuters on Monday, called for UNMIS to increase patrols in the area and to increase support to local officials to try to improve the dire security situation.

An estimated 2 million people were killed and some 4 million people were displaced in the two-decade-long north-south war over ideology, race, religion and oil. A separate conflict in Sudan's western region of Darfur is still continuing.

Sudan