Peacekeepers came under fire in Sudan's Darfur region while they searched for colleagues missing in a flood, the mission said Thursday, reporting the third attack this month against Blue Helmets.

The attack by "unknown armed men" happened Tuesday about seven kilometres (four miles) northeast of Misterei, a West Darfur town near the border with Chad, said Rania Abdulrahman, a media officer with the African Union-United Nations Mission in Darfur (UNAMID).

The peacekeepers repelled the assailants and there were no casualties, she said, adding that the search continues for four missing UNAMID troops who were swept away in a flash flood Sunday.

Violence in Darfur and against UNAMID has worsened this year.

Three peacekeepers were shot and wounded Monday in East Darfur, in an area where two Arab tribes fought deadly battles this month.

On 12 August, a UNAMID police patrol was ambushed in the East Darfur capital Ed Daein, but there were no injuries, UNAMID said earlier.

Hundreds of people have died in tribal fighting in Darfur this year, largely between Arab groups, which analysts say are acting outside government control.

Seven peacekeepers were killed in an ambush last month. It was the worst-ever attack in the mission's five-year history.

The UN Security Council then ordered a review of UNAMID operations, in light of deteriorating security.