Rebels in Chad attacked an eastern frontier town on Tuesday in a raid the government said was ordered by Sudan and violated a peace pact signed last month by the two oil-producing neighbours.

Sudan's armed forces denied any role in the attack on Ade by Chad's rebel National Alliance, which said its fighters struck from inside Chadian territory without crossing the border.

The latest clash and recriminations signalled a renewal of tensions between the two African states caught up in the conflict in Sudan's border region of Darfur, where around 200,000 people have been killed since 2003, experts say.

Chad's government said the attacking rebels crossed from Sudanese territory and were "under orders from the Sudanese regime" in direct violation of a peace accord signed last month in Senegal by the presidents of both countries.

Under the March 13 accord, President Omar Hassan al-Bashir of Sudan and Chadian President Idriss Deby pledged not to allow their territory to be used by rebels hostile to their governments. Chad has long accused Bashir of backing Chadian rebels, while Khartoum says Chad supports Darfuri insurgents.

"President Bashir has not changed and continues to try to destroy Chad. We call on the international community to bear witness that, despite the Dakar accord, he is attacking us again today," Chadian Prime Minister Nouradine Delwa Kassire Coumakoye said in a briefing to foreign ambassadors in N'Djamena.

He said the rebel raiders travelled 78 km (50 miles) from inside Sudan to attack Ade across the border.

Sudan's armed forces quickly denied the Chadian accusation and said they were respecting all existing peace accords.

"We absolutely deny this. Sudan did not support any Chadian rebels in attacking the town of Ade. Sudan's armed forces has no hand in what is happening in Chad - this an internal matter," a Sudanese military spokesman told Reuters in Khartoum.

Ali Gadaye, spokesman for the Chadian rebel National Alliance, said a three-hour battle followed the attack on Ade.

But he denied the rebel force had crossed from Sudan.

"That's the Chadian government's same old song," Gadaye said, adding the rebels had advanced from positions inside Chad.

BROKEN PEACE ACCORDS

Details of casualties were not immediately available.

Chad's government said its forces had beaten off the rebel attack and were mopping up the fleeing enemy.

Gadaye said the rebels had broken off the assault when government reinforcements, including pro-Deby Sudanese Darfuri rebels known as "Toroboro", arrived from the north. Rebel forces were still around Ade, he added.

A spokesman for a European Union military force deployed in eastern Chad to protect refugees and civilians told Reuters he had no immediate information about the rebel attack on Ade.

The March 13 accord signed in Dakar, brokered by Senegalese President Abdoulaye Wade and witnessed by U.N. Secretary-General Ban Ki-moon, was the latest in a string of peace pacts between the two neighbours. Previous deals had all collapsed amid renewed fighting on both sides of the border.

Chadian rebel groups, which have fought for more than two years against Deby, said the Dakar accord did not concern them and vowed to continue their efforts to topple him.

The rebels attacked the Chadian capital early in February, but were held off by Deby's forces, which received intelligence, medical and logistical backing from French troops and planes stationed in Chad under a cooperation accord.

Gadaye said French military planes had flown over the rebel positions at Ade on Tuesday.