DUK PADIET, SUDAN —The word went out on a Friday. Chibetek was coming, with warriors and a grudge to settle.

The whole village sprang into battle mode. Boys grabbed rusty rifles, women ran to the river to hide in the water, old men stood sentry on the village outskirts, training their yellow, rheumy eyes on the vast savannahs and malarial swamps that have kept this region cut off for decades.

And when the warriors did come, the villagers said, there were hundreds of them, maybe thousands, pouring through the chest-high elephant grass with machine guns and rocket-propelled grenades, dressed in crisp new uniforms that implied a level of military organization never seen before.

“;This was no cattle raid,”; said Majak Piok, a village elder.

Southern Sudan, one of the least developed and most war-haunted parts of Africa, is at a critical point, gearing up for a vote on independence that will likely break an already volatile Sudan in two. It is the culmination of decades of civil war and a U.S.-backed peace treaty to end it, but as the long-savored day approaches many south Sudanese fear another devastating war is on the horizon.

More than 2,000 people have been killed this year in ethnically driven battles like the recent one in Duk Padiet. “;Tribal war”; is what the villagers here call it, but southern Sudanese leaders and some U.N. diplomats suspect these are not simply local grievances playing out at gunpoint.

Instead, they point to a recent influx of weapons in the area, saying it suggests that northern Sudanese officials are arming various factions - much as they have done before - in a plot to plunge the south into chaos so that the independence referendum, scheduled for 2011, will be delayed or even called off.

The northern politicians, who control the country, ardently deny these accusations, and there is no concrete proof of meddling. But the stability of Sudan, the largest country in Africa at nearly 1 million square miles, could be at stake.

More than 2 million people died during the civil war that ended with the 2005 peace agreement, and if a new north-south conflict were to erupt again it could drag in militants from Darfur, the Nuba mountains, eastern Sudan and other corners of the country.

This time, the center might not hold, many analysts say, given how combustible Sudan's politics have become. The president, Omar Hassan al-Bashir, has been indicted for war crimes; the nation is bracing for a contentious election in April; huge supplies of weapons continue to flow in; and militaries in the north and south are on high alert, especially in unresolved border areas.

Already in the south, villages are getting razed, children abducted and thousands of destitute civilians are streaming into refugee camps in scenes reminiscent of the Darfur conflict, which, after years of raging, is comparatively quiet.

“;This,”; said David Gressly, the top U.N. official in southern Sudan, “;is the cockpit”; of violence. He swept his hand across a map showing Jonglei state, where Duk Padiet was attacked by a renegade commander named Chibetek. Several other recent massacres have occurred in the area as well.

Cattle rustling and small-scale skirmishes have gone on for ages, Gressly said, but this year there was an unusual “;ease and availability of ammunition.”;

The north has a well-documented history of funneling arms to southern Sudan and pitting southerners against each other, typically along ethnic lines. And there are billions of dollars of oil in the south, which the north clearly does not want to lose.

But the Arab-dominated north is also a convenient scapegoat, and northern officials complain of being portrayed as “;the bogeyman.”; Since southern Sudan was granted some autonomy in 2005, its leaders have disappointed their people in many ways, with bungled disarmament schemes and staggering corruption.

Recently, $200 million earmarked for grain vanished from the south's finance ministry at a time when drought and conflict-related displacement have driven more than 1 million southerners to the brink of famine.

The land here is unforgiving, and in places looks like a junkyard of war, with burned-out tanks and shot-down jet fighters sinking into the weeds. During the colonial period, the British carved the area into zones of influence for the few European missionaries willing to brave the rampant malaria, typhoid and unyielding heat.

The people here are strikingly different from their countrymen in the Islamic north. Most are animist or Christian, extremely tall - it's not uncommon to meet seven-foot men - and wedded to a life revolving so closely around cows that people name children after them.

Even before Sudan was granted independence in 1956, southerners were chafing for their own country. War broke out several times, and in the late 1980s, the Sudan People's Liberation Army emerged as the strongest, multi-ethnic guerilla force.

But just as the SPLA was about to capture major cities, the rebels - instigated by northern politicians - violently split. Some of the worst atrocities during the civil war were south-on-south violence, like the so-called Bor Massacre in 1991, when Nuer warriors slaughtered 2,000 Dinka. It was essentially a civil war within a civil war.

Many people here say it is beginning to feel like that now.

In Duk Padiet, the ground is scarred by rings of ash from huts burned down during the attack in September. The people here are Dinka. The well-armed attackers were Nuer.

More than 160 people were killed, including local policemen, women, children, and a Somali trader and Darfurian shopkeeper buried in the same shallow grave because no one knew exactly where they were from.

Nuer leaders do not deny that Nuer warriors killed dozens. But they say that the Dinka-led local government was blockading a road into Nuer areas and not allowing the Nuer access to the river.

“;The Nuer felt the government was ignoring them,”; said Solomon Pur, a Nuer youth leader.

In the past, these rivalries occasionally became violent, with maybe a few warriors killed on each side. But the recent attacks seem more like infantry maneuvers. In one massacre this March, 17 villages were besieged and more than 700 people killed, according to U.N. officials.

Diing Akol Diing, a county commissioner near Duk Padiet, keeps pictures of victims on his computer: Children with bullet holes in their chest. Old women curled up in pools of blood. Emaciated militia fighters in smart new camouflage.

“;This is madness,”; he says.

He clicks on a photograph of a dozen people wrapped in blankets, buried in a ditch.

“;Mass graves?”; he says. “;We've never had mass graves.”;