Sudan's Darfur region is facing a new wave of killings and rapes, with fighting between rebel factions displacing thousands of villagers despite a recent peace agreement, the U.N. humanitarian chief said.

Humanitarian workers are being attacked every day, and "new front lines are opening all the time in new areas," Jan Egeland told a news conference Tuesday.

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He accused the Sudan Liberation Army faction led by Minni Minnawi, the only rebel group to sign the May 5 peace agreement with the government, of attacking villages held by SLA splinter groups.

"The infighting has displaced 8,000 civilians over the last 10 days alone," Egeland said. "The attacks have included indiscriminate killings, mass rape, beatings, looting and the burning of villages."

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Minnawi has denied his forces are responsible for the upsurge in fighting and new atrocities.

The Darfur conflict began in early 2003 when members of ethnic African tribes revolted against Sudan's -led government, which is accused of responding by unleashing Arab militias known as the Janjaweed who have been blamed for the worst atrocities. Khartoum denies involvement, but has committed to disarm the Janjaweed under the peace deal.

Egeland said there were reports of government forces supporting the latest attacks against the SLA splinter groups.

"It is heartbreaking to see what the SLA groups rightfully accused the Janjaweed of doing, they are now doing themselves to the civilian population caught in the crossfire," said Egeland, the U.N. undersecretary-general for humanitarian affairs.

He also warned about reports of Sudanese security and armed forces painting their helicopters white, the same color as U.N. and African Union helicopters.

"This is again a violation of international principles and poses a direct threat to U.N. and NGO staff who go on the white helicopters that are neutral, impartial and should not be attacked," he said.

Egeland said the region needed massive humanitarian assistance but the U.N. faced financial, security and access problems. He urged donors to be more generous and called on opposing parties to talk peace instead of escalating fighting.

Egeland said U.N. peacekeepers are desperately needed in Darfur because a 7,000-strong African Union force can't effectively protect civilians. The Sudanese government has refused to approve the handover, saying a U.N. force would bring Westerners to the country. But Egeland said only African, Middle Eastern and Asian countries have offered troops.

More than 180,000 people have died and 2 million have been made homeless since the conflict began. The fighting has also spilled across the border into Chad.