TURALEI, Sudan-- A top U.S. official warned of a humanitarian crisis Friday over the north's invasion of a disputed territory as southern towns taking in tens of thousands of fleeing villagers were running short of food, fuel and shelter.

County Commissioner Dominic Deng said Friday that up to 40,000 people have arrived in Turalei, a town to the south of the disputed region of Abyei. He said at least 80,000 people have fled Abyei, a zone about the size of Connecticut which northern Sudan invaded last weekend.

On a visit to Turalei on Friday, the top U.S. official in Southern Sudan, Barrie Walkley, said "we have a perfect storm" creating a humanitarian crisis. Sudan's north is blockading border crossing points, preventing food and fuel from getting to the south. Militias are attacking southern forces, and the northern army displaced tens of thousands of people by invading Abyei, he said.

Lise Grande, the U.N.'s top humanitarian official in Southern Sudan, said there are not enough stocks in the area to supply all the fleeing families with food and shelter. The fuel shortage is greatly hampering relief efforts, she said.

"It's double the number of people we were planning for," she said. "We have to face the fact that if they are here for a while then what we have is not enough."

Martha Abiem Deng fled to Turalei with a dozen children, four her own and the rest nieces and nephews. She sat under a tree on a mat and gestured to one small jerry can. Her whole family must share the water within it.

"We don't have any money and there is no food in the market anyway," the 49-year-old said.
Market stalls in town were completely empty of food. The only items for sale were cigarettes and phone chargers.

Both northern and Southern Sudan stake a claim to Abyei, a fertile grassland near several oil fields. Fighting between north and south broke out last week, and northern troops moved in with force.

Southern Sudan's president says the south will not respond militarily and risk a resumption of the country's civil war. More than 2 million people were killed during war, which ended with a peace deal in 2005.

The U.S. ambassador to the U.N., Susan Rice, said Thursday that the north's movement into Abyei appears to have been premeditated.

Rice said government forces seem to have used an attack by southern forces on a convoy of government soldiers from the north last week as a "pretext" to move into Abyei, the border town between Sudan's Arab-dominated north and mainly ethnic African south.

North and south Sudan ended more than two decades of civil war in 2005 with a peace deal that promised both Abyei and the south a self-determination vote. The south voted overwhelmingly in January to secede and becomes an independent nation July 9. Abyei's vote never happened, so its future was being negotiated by the north and south.

Human Rights Watch says the Sudanese government urgently needs to halt looting and destruction of civilian property by its forces in the town of Abyei and hold those responsible to account. It also demanded that the government allow United Nations peacekeepers access to the entire Abyei area.