Unknown gunmen killed three peacekeepers and seriously wounded one in the Jebel Marra region of western Sudan's Darfur on Monday, the UN-African Union Mission in Darfur (UNAMID) said.

"The soldiers from a UNAMID Protection Force Battalion, who were providing security to civilian engineers working on a UNAMID team site at the time, came suddenly under heavy gunfire at approximately 11:30 a.m. (0830 GMT) from more than 20 assailants in camouflage battle dress," said a statement by UNAMID, a copy of which was made available to Xinhua.

The peacekeepers returned fire and engaged the attackers in a firefight which lasted almost an hour, killing three of the assailants, while the remainder of the attacking force fled the scene, stealing a vehicle, the statement added.

UNAMID Deputy Joint Special Representative (DJSR) Mohamed B. Yonis expressed his outrage at this act of wanton violence, according to the statement.

Praising the courage of the peacekeepers, the DJSR stated that UNAMID would not be intimidated.

"Our mission will continue to carry out its mandate, which is to bring peace and security to the people of Darfur," he said.

The mission strongly condemned these cowardly acts of violence against its peacekeepers, calling on all parties to ensure the safety of UNAMID personnel in the region and pointing out that any attack against peacekeepers is a war crime, the statement said.

In the meantime, Ali Hamati, a UNAMID spokesperson, told Xinhua that the seriously wounded soldier has been transported to the Mission's hospital in Nyala in South Darfur State.

Hamati further condemned the incident and urged the Sudanese government to open an urgent investigation and work to bring the perpetrators to justice.

The last attack on UNAMID peacekeepers occurred in May, when two Egyptian troops were killed and three injured in an ambush in South Darfur.

Monday's events bring the number of fallen UNAMID peacekeepers to 27, including 24 military personnel and three police officers.