* Large parts of Abyei town left empty: MSF
* U.N. reinforces, north/south leaders form committee
KHARTOUM, March 4 (Reuters) - Tens of thousands of people have fled Sudan&${esc.hash}39;s contested Abyei border town, leaving large parts of it empty, aid workers said on Friday, after a surge in fighting left dozens dead.
The United Nations said it was moving more than 100 new peacekeepers into the area to help quell violence that has raised fears for the stability of Sudan&${esc.hash}39;s oil-producing south in the countdown to its independence in July.
Senior U.N. officers met with northern and southern government leaders in Abyei on Friday and agreed to set up a joint committee to enforce an existing peace agreement in the territory, U.N. spokeswoman Hua Jiang added.
Both north and south Sudan claim the central, fertile Abyei area and their troops have clashed there, even after a 2005 peace deal officially ended decades of civil war.
The latest fighting broke out on villages north of Abyei town on Sunday. Estimates of the death toll have varied widely.
"Since yesterday (Thursday), tens of thousands of people have fled the town, leaving it mostly empty," the aid group Medecins Sans Frontieres in a statement.
MSF said it had treated 21 people for gunshot wounds on Wednesday south of Abyei town and was trying to reach other patients.
Most of the women and children in Abyei town had now left and headed south, fearing more violence, Abyei Catholic priest Peter Sulliman told Reuters.
North Sudan blamed the south for provoking several clashes between northern Arab Misseriya nomads and police in villages occupied by the south-linked Dinka Ngok people.
Northern army spokesman Al-Sawarmi Khaled said the south had failed to pull out a force of armed southern police, state media reported.
Abyei is supposed to be patrolled by joint north-south police and military units, as well as by U.N. peacekeepers.
Southern Dinka officials have accused Khartoum of sending soldiers and militias to fight alongside the Misseriya to attack villages and clear their populations from the area.
Tensions have been exacerbated by the onset of the migration season, when the Misseriya drive their livestock through Abyei into the south searching for pasture.
The U.N.&${esc.hash}39;s Jiang said the world body had decided to send an extra company of peacekeepers to reinforce the four companies already stationed in Abyei. A company comprises 100-130 soldiers, she said.
The new joint committee, including representatives from the northern and southern armies, would make sure peace deals agreed after fighting in January would be implemented, she added.
Those deals guaranteed the migration and promised the withdrawal of the southern police, among other issues.
South Sudan is due to secede on July 9 after 99 percent of its voters chose independence in a referendum in January -- a vote promised under the 2005 accord.
Abyei&${esc.hash}39;s residents were promised their own referendum on whether to join north or south. That plebiscite never took place after northern and southern leaders failed to appoint an organising commission or agree on who was qualified to vote.
(Reporting by Andrew Heavens)
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