The situation remained too tense to deliver relief aid to the town, where a high-ranking delegation of government, rebel and United Nations officials arrived Thursday to contain the crisis after days of heavy fighting between the Sudan People's Liberation Movement and government forces.
More than 150 people have been killed and 400 severely injured in Malakal after days of fighting between former rebels and government forces, a U.N. official confirmed on Saturday.
The U.N. mission in Sudan appealed for volunteer nurses and supplies and warned that corpses strewing the Nile River were contaminating one of the town's main sources of drinking water.
"There are over 150 dead from all sources," U.N. official Peter Maxwell told The Associated Press in a telephone interview from Malakal, a port town located on the Nile some 400 miles south of the Sudanese capital, Khartoum.
Maxwell, the field office manager in Malakal for the U.N. mission in Sudan, said the situation in the town was "fairly calm" since a cease-fire was brokered Friday.
Most of the dead appeared to be combatants from both sides, but at least two dozen appeared to be civilians, Chris Imana, area coordinator for the Christian aid group World Vision, told The Associated Press.
Aid workers said the fighting began when a militia allied to the government tried to kill a local SPLM commander. The former SPLM rebels then retaliated against the town's army commander. Clashes evolved into large-scale battles on Tuesday, with artillery barrages, tanks and armored personnel carriers battling in downtown Malakal, a town of about 150,000 people.
Renaldo Fiocco, an aid worker for the French group Medecins du Monde, said, "This wasn't little guerrilla shooting, this was war."
In a telephone interview Fiocco said the worst battles occurred in the center of the town, with artillery barrages, mortar rounds and hours of shooting.
In New York, U.N. Secretary General Kofi Annan was "deeply concerned about the reports of heavy fighting," between the army and the former rebels, his spokesman Stephane Dujarric said earlier this week.
A January 2005 peace deal ended 21 years of civil war between north and south Sudan, but the situation in Malakal has remained volatile. The port town, which lies on the Nile river close to Sudan's richest oil fields, is located next to the north-south boundary.
Nonessential U.N. staff and most aid workers have been evacuated.
The U.N. has some 10,000 peacekeepers in south Sudan to monitor the peace agreement and help reconstruct the ravaged region.
The clashes in Malakal "constitute a serious violation of the security arrangements" under the peace deal, Annan's spokesman said.
The U.N. said it could not confirm any death toll, but would investigate causalities in what appeared to be one of the gravest breaches of the 2005 cease-fire.