ADDIS ABABA  - Sudan and South Sudan broke off security talks on Thursday after failing to agree on a demilitarised zone along their disputed border to help prevent them slipping into outright warfare.

The African neighbours came close to war when a border dispute in April saw the worst violence since South Sudan split from Sudan in July under a 2005 peace deal that ended decades of civil war.

Both countries, which accuse each other of supporting rebels in the other's territory, returned to African Union-mediated negotiations last week, the first direct talks since the border clashes.

After 10 days of talks, the two sides were unable to agree where to draw a demilitarised buffer zone along the 1,800-km- (1,200-mile-) long border.

Khartoum's delegation accused South Sudan of making new land claims, most importantly to the Heglig oil field whose output is vital to Sudan's battered economy. The southern army had temporarily occupied Heglig during the recent fighting.

"The border is based on a map that we have been using for the past six years (since the 2005 peace deal was signed), but they (South Sudan) have included five areas within their border," Sudanese Defence Minister Abdel Raheem Mohamed Hussein said.

"We consider it as a hostile action," he told reporters in Addis Ababa, where the talks took place.

To back its claim to the field, Khartoum has cited a 2009 ruling by the Permanent Court of Arbitration in The Hague on Abyei, another disputed area. The court issued maps that put Heglig in the north.

Juba contests Khartoum's claim, citing an internal boundary marked from the British colonial rule that ended in 1956, and the ethnicity of the local population.

There was no immediate word from South Sudan but members of Juba's delegation confirmed talks on border security had ended for now with no agreement and no new date scheduled.

Despite the lack of progress, Hussein said both sides had renewed pledges to end hostilities during the talks.

"We will continue attending these talks but the (African Union) panel will now take time and invite (us back)," he said.

Sudan accuses South Sudan of supporting rebels fighting the army in two southern border states. Juba denies the claims and says Khartoum funds militias on its side of the border.

Diplomats and the Sudanese foreign ministry said talks on a future status for Abyei, another contested border area, would probably continue for the next few days.

Both countries are at loggerheads on a string of issues such as oil payments. Landlocked South Sudan took three-quarters of Sudan's oil production -- the lifeline of both economies -- but needs to sell its crude through northern export facilities.

Both countries have failed to agree on a transit pipeline fee and Juba has shut down its entire oil output of roughly 350,000 barrels after Khartoum started seizing southern oil as compensation for what it calls unpaid fees.

Some two million people died in the civil conflict between north and south, waged for all but a few years between 1955 and 2005 over ideology, ethnicity, religion and oil.