Gunmen ambushed a United Nations peacekeeping team Saturday in Sudan's western region of Darfur, killing seven and wounding another 17 in the deadliest ever single attack on the international force in the country.

The assault included sustained heavy fire from machine guns and possibly rocket-propelled grenades, targeting the force some 25 kilometers (15 miles) west of the town of Khor Abeche, U.N. forces spokesman Chris Cycmanick said. Reinforcements later arrived to rescue the wounded, who included two female police advisers, the force said in a statement.

It wasn't immediately clear if any civilian personnel accompanied the team into the ambush, Cycmanick said. He declined to give the nationalities of those killed and wounded in the attack. About 40 countries have contributed military personnel or police to the peacekeeping force.

No group immediately claimed responsibility for the assault. A February report by a U.N. panel of experts said that some armed opposition groups angry about the presence of peacekeepers have called the force "a legitimate target."

Peacekeepers have been targeted by assailants in the past in the region since the international force began its work there in 2008. In the last fatal attack, gunmen shot dead a Nigerian peacekeeper in April in East Darfur State. Before Saturday's attack, 150 people associated with the U.N. mission in Darfur had been killed while on duty in the region, according to the force's website.

The joint African Union-U.N. peacekeeping force, dubbed UNAMID, was established to protect civilians in Darfur, but also contributes to security for those providing humanitarian aid, verifying agreements, political reconciliation efforts and promoting human rights. It has about 16,500 troops and military observers and over 5,000 international police.

Darfur has been gripped by bloodshed since 2003 when rebels took up arms against the government in Khartoum. Fighting also erupts between tribes in the region. More than 300,000 people have been killed in the conflict.

Unrest continues to grip the region. About 300,000 people have fled fighting throughout Darfur in the first five months of this year, the U.N. has said.

"The mission condemns in the strongest possible terms those responsible for this heinous attack on our peacekeepers," said Mohamed Ibn Chambas, a joint special representative of the force. "The perpetrators should be on notice that they will be pursued for this crime and gross violation of international humanitarian law."

More than 100 U.N. peacekeepers were killed last year alone on duty in the Darfur and Abyei regions of Sudan, Congo, Ivory Coast and other countries. Eight more civilian contractors, such as pilots, also died on deployment with peacekeeping missions in 2012.

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Associated Press writer Edie Lederer in New York contributed to this report.

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Jon Gambrell can be reached at www.twitter.com/jongambrellAP.