Four peacekeepers belonging to the United Nations-African Union Mission in Darfur (UNAMID) have been kidnapped by unknown gunmen in the restive western Sudanese region of Darfur, a UNAMID source told Xinhua on Tuesday.

The anonymous source said the four South African peacekeepers, two male and two female, were stopped by some 10 gunmen when they were driving from their working site to their private accommodation near Nyala, the capital city of the South Darfur state, on Sunday.

The source quoted witnesses as saying that the four policemen were forced to step off their vehicle at gunpoint.

No armed group in Darfur has made contacts with the UNAMID to claim responsibility for the kidnapping, the source noted.

UNAMID spokesman Noureddine Mezni has refused to confirm or deny the kidnapping, noting that the four peacekeepers were reported missing since Sunday.

"I can not confirm or deny this report (of the kidnapping), I have no confirmations on what had happened," the spokesman said on Tuesday.

Earlier, the UNAMID said four peacekeepers of the mission were missing since Sunday evening in Darfur.

"The peacekeepers' last movement was reported at 4:00 p.m. (1100 GMT) on April 11, 2010, as they departed their team site just outside of Nyala, South Darfur, on a 7-km journey back to their private accommodation," the peacekeeping mission said in a statement.

"There have been no sightings of our staff and we are deeply concerned for their well-being," said UNAMID Joint Special Representative Ibrahim Gambari, who had held direct contacts with Sudanese government officials over this issue.

UNAMID has mobilized its resources in the region and is working closely with the Sudanese government and local authorities in the search for the missing peacekeepers, according to the statement.

More than 20 peacekeepers of the 26,000-strong UNAMID have been killed since the UNAMID took over from the African mission on Dec. 31, 2007.

The incident occurred while a three-day polling has been taking place since Sunday in the troubled region as part of the multi-party general elections, the first of its kind in the country in more than 20 years.