KHARTOUM (Reuters) - Sudan's government and Darfur's most powerful rebel force accused each other of breaking a recently-signed ceasefire on Monday, undermining already stalled peace talks between both sides.

The insurgent Justice and Equality Movement (JEM) told Reuters that Sudan's army bombed its positions in Darfur, close to the Chad border, from midnight through Monday morning, wounding six civilians and killing their livestock.

Sudan's army denied launching any attacks on JEM and a senior government official accused the rebels of seizing new territory in the remote western region, against the terms of the same agreement.

Sudan's president Omar Hassan al-Bashir declared the seven- year Darfur conflict over after his government signed a ceasefire and initial peace deal with JEM in the Qatari capital Doha in February.

But further talks quickly stalled after JEM objected to Khartoum starting parallel discussions with another rebel group.

The peace push was also marred by reports of clashes between Khartoum and a third insurgent force in the Jabel Marra area.

Violence surged in 2003 after JEM and other mostly non-Arab rebels took up arms against Sudan's government, accusing it of neglecting the development of the region.

Khartoum mobilised mostly Arab militias to crush the revolt, unleashing a wave of violence that Washington and some activists have call genocide, a charge Sudan's government rejects.

"The bombing started at midnight and continued this morning ... These people (the government) are not interested in finding a political solution to the problem," said JEM spokesman Ahmed Hussein Adam, speaking from Qatar by phone.

Adam said government planes bombed JEM positions around the North Darfur areas of Abu Hamra, Furawiya and Jabel Moun.

He said the rebel force was "considering its position" over future talks but there were no immediate plans to walk out of negotiations.

Sudan dismissed JEM's accusations. "The Sudanese Army is committed to the ceasefire it has signed with JEM. It has not bombed any JEM positions," an army spokesman told Reuters.

JEM's main negotiator Ahmed Tugud told Reuters both sides were in stalemate over details of how the ceasefire would be monitored and managed, together with other issues he did not want to discuss in the media.

Khartoum's main Darfur negotiator Ghazi Salaheddin said JEM has been looking to take more territory.

"They (JEM) have been fanning out in the area and trying to establish themselves in Kulbus and Jabel Moun which is a violation of the ceasefire declaration," Salaheddin told reporters in Khartoum.

Darfur's under-equipped joint U.N./African Union UNAMID peacekeeping force said it could not confirm whether any fighting took place. "We are not present in the area so we can not confirm," UNAMID spokesman Noureddine Mezni told Reuters.