A rebel group in Darfur says Sudanese government forces have launched new attacks in western Darfur despite claims from Khartoum that its troops have stood down in the troubled region for several days. Nick Wadhams has more from Nairobi.

In recent days, the Sudanese government has heatedly denied allegations that its troops are on the attack in Darfur, arguing that such claims have been fabricated by aid agencies with an agenda. It says it is determined to start peace talks with the rebels and bring peace to the region at last.

Yahia Bolad, a London-based spokesman for the SLA, says his group wants to adhere to a ceasefire but had no choice but to fight the troops and repulse them.

"They are sending aircraft and also helicopters to western Darfur in order to continue their attack on our people on the ground," Bolad said. "And there is an attack from the government in our areas yesterday. The government troops they attack two villages. And our troops response the attack, the government troops withdraw from the village and turn back."

Bolad says there he has no word on the number of people who were killed or wounded in the latest attacks, but said there were casualties.

Sudanese officials could not be reached for comment about Bolad's claims. But on Tuesday, U.N. Secretary-General Ban Ki-moon said he was concerned about an escalation in violence in Darfur that had killed hundreds of people in the last few weeks.

Officials had hoped that a U.N. Security Council decision in late July to send a new African Union and United Nations peacekeeping force to Darfur sometime next year would ease the conflict. Some 200,000 people have died in four years of fighting.

But neither the council's decision, nor a meeting earlier this month in which some rebel groups agreed to a united front for future talks, have eased the tension.

Bolad says his faction of the SLA will not even think about giving up its weapons until U.N. forces are on the ground.

"For now we have our commitment to the ceasefire," Bolad said. "Only in self defense. But when the U.N. troops come and they bring stability and protect our people on the ground at that point we can discuss the issue of our weapons."

United Nations and African Union officials have said that they hope peace talks will begin sometime in October. However, with the continuing violence, that timetable is looking less and less likely.