At least seven peacekeepers from the joint African Union-United Nations mission in the Sudanese region of Darfur has been killed in an attack blamed on Janjawid fighters, a UN official said.

Twenty-two others from the Unamid contingent were injured after the ambush on Tuesday in North Darfur state, southwest of the mission's headquarters in El Fasher, the official said.

Seven of the wounded soldiers were in a serious condition after the incident is Um Hakibah, about 100 kilometres from Shangil Tobayi.

Michele Montas, a spokeswoman for Ban Ki-moon, said the UN secretary general "condemns in the strongest possible terms this unacceptable act of extreme violence"

She said that the attack on a joint military and police patrol lasted two hours and the assailants used heavy weapons.

Suna, Sudan's official news agency, reported that the attackers were travelling in a convoy of about 40 vehicles.

The 9,000-strong United Nations-AU force has been in place in Darfur since earlier this year.

It is authorised to have 26,000 members, but has suffered from shortages of staff and equipment and a lack of co-operation from the Sudanese government.

Unamid says that the US and other governments have not supplied the helicopters, surveillance aircraft, military engineers and logistical support needed for it to operate effectively in the region.

Last month, four members of the force were assaulted and held at gunpoint in Darfur, with one staffer stripped of his belongings, according to a Unamid statement.