Khartoum: Some 200 gunmen on horseback and in SUVs ambushed peacekeepers from a joint UN-African Union force in Sudan's Darfur region, killing seven in fierce gunbattles that lasted more than two hours, UN officials said on Wednesday.

UN Secretary-General Ban Ki-moon's office said 22 peacekeepers were wounded in the attack Tuesday on a joint police and military patrol investigating the killing of civilians in North Darfur state. It was the worst attack on the combined UN-AU peacekeeping force since it deployed in December.

A group of about 200 assailants riding horses and driving 40 SUVs mounted with anti-aircraft and anti-tank weapons exchanged gunfire for more than two hours with the peacekeeping force that included 61 Rwandan soldiers, the UN said.

Five Rwandan soldiers and two police officers, one from Ghana, the other from Uganda, were killed. At least seven of the wounded were in serious condition, Ban's office said.

"We are outraged by the attack," Shereen Zorba, deputy spokeswoman of the UN-AU mission known as UNAMID, told The Associated Press. "We are not part of the conflict, but a tool to alleviate the suffering of civilians. We try to establish some level of peace and security in the ground. But to drag us in to be part of the conflict is unjustifiable."

The gunmen attacked the peacekeepers in an area called Umm Hagiba, about 60 miles from UNAMID's camp in North Darfur. Zorba said the ambush occurred as the peacekeepers were returning to their camp after investigating the recent slayings of two rebels affiliated with the Sudan Liberation Army. She declined to say who was behind the attack.

Another UN official said drivers in the UNAMID convoy lost control of their vehicles when they came under attack. Members of the unit then ran in different directions and the attackers chased them, the official added, speaking on condition of anonymity because he was not authorized to disclose details of the attack to the media.

State Department spokesman Sean McCormack said the U.S. was working within the UN Security Council to issue a presidential statement on the attack.

"We and others in the international community want to see those responsible for this attack held to account," he said.

The UN Security Council quickly issued a statement condemning the attack "in the strongest terms" and calling on the perpetrators to be brought to justice.

The attack was the deadliest on Darfur peacekeepers since October, when 10 African Union peacekeepers were killed in an ambush on a military base in Haskanita in North Darfur state. Rebels were blamed for that attack.

That attack came before the joint United Nations-AU force took over peacekeeping duties from an all-AU force in the remote western region of Sudan in December with about 9,000 soldiers and police officers.

It is authorized to have 26,000 members, but has contended with chronic shortages of staff and equipment and less-than-adequate cooperation from the Sudanese government.

The peacekeeping force has been unable to persuade the US and other governments to supply attack and transport helicopters, surveillance aircraft, military engineers and logistical support it needs to safely navigate Darfur.

Actress Mia Farrow, a leading activist for peace in Darfur, laid some of the blame for the attack on the international community for allowing the Sudanese government to block full deployment of UN peacekeepers in Darfur.

"The international community is failing to support the peacekeeping mission in Darfur and as a result we are watching it fail," she said. "The U.S., the UN and all the nations of the world are once again allowing the Khartoum regime to dictate the conditions under which Darfur's victims can be protected."

Last month, four UN-AU staffers were assaulted and held at gunpoint in Darfur. One of the staffers was stripped of his belongings, kidnapped briefly and then released by Arab militiamen on horseback, according to a statement from the joint force.

In May, an Ugandan officer was found fatally shot in a vehicle operated by the UNAMID force in North Darfur — the first UN-AU peacekeeper killed since the mission deployed in January. UNAMID had described the killing as "an act of cold blooded murder."

UN peacekeeping chief Jean-Marie Guehenno has said there was an alarming increase in violence in the Darfur, which also spread recently to the capital Khartoum and said it could escalate further.

Zorba urged the international community to send the mission additional equipment including tactical and surveillance helicopters.

The Darfur conflict has claimed up to 300,000 lives and uprooted 2.5 million people since ethnic African rebels took up arms against the Arab-dominated government in 2003. Critics accuse Sudan of arming janjaweed Arab militias that have terrorized Darfur villages — a charge Khartoum denies.