But while welcoming the accord, Security Council members raised new concerns about Sudan where conflict in South Kordofan and Blue Nile states and deadlock in the Darfur war have added to fears of a growing crisis.

Khartoum government forces occupied Abyei in May and more than 110,000 people fled their homes to South Sudan, which also claims the border region.

The Sudanese and South Sudanese governments reached the latest accord during talks in Addis Ababa, Edmond Mulet, UN assistant secretary general for peacekeeping, told reporters after a Security Council meeting on Sudan.

The accord was brokered by an African Union mediation panel led by former South African president Thabo Mbeki, Mulet said.

"They have agreed that between September 11 and 30 there is going to be a redeployment or withdrawal of the troops" from Abyei by both sides, he said.

Sudan had previously agreed to withdraw its troops when UN peacekeepers arrived. The UN force of more than 1,700 Ethiopian troops have been in Abyei for several weeks but Khartoum had kept their forces there. Some South Sudan troops have also remained in the territory.

Mulet said the Khartoum government had insisted there had to be an administration in Abyei before it left, but has now agreed to withdraw.

The fate of Abyei was left undecided when north and south Sudan split in July. Both sides claim the region, which did not hold a referendum on its future in January when South Sudan voted to break away.

Despite the accord, western governments raised new concerns about fighting in neighboring South Kordofan and Blue Nile states where the Sudanese government has severely restricted access to international aid agencies.

The Security Council met as UN advisors on the prevention of genocide said they were "gravely concerned" about reports of air attacks by the Sudanese air force on civilians in South Kordofan.

The advisors, Edward Luck and Francis Deng, highlighted reports of aerial bombardments in the Nuba mountains region of Kordofan. "Latest reports indicate that the violence has spilled over into neighboring Blue Nile state resulting in tens of thousands of civilians fleeing to neighboring states and across the border into Ethiopia," the two said in a statement.

Britain's UN ambassador Mark Lyall Grant said that the Abyei accord was encouraging but added: "Nonetheless we are deeply concerned about a number of issues over South Sudan and Sudan."

He said the Khartoum government was still putting up "obstacles" to the UN mission in Abyei. "There is a very serious humanitarian situation in South Kordofan and Blue Nile to which humanitarian access is severely restricted if not entirely denied."

Darfur "is still very bad" and the two Sudans have still not settled their border and the sharing of oil revenues, said the envoy.

Lyall Grant and Germany's ambassador Peter Wittig said the UN Security Council would have to pay greater attention to Sudan in coming weeks.

Both said the 15-nation council should avoid separate talks on the individual conflicts in Sudan and increase general pressure on the Sudan government and South Sudan to reduce tensions.

A two decade civil war between the north and south up to 2005 left an estimated two million dead.

Copyright AFP (Agence France-Presse), 2011