KHARTOUM, April 15 (Xinhua) -- A rebel group in Sudan's western region of Darfur has declared responsibility for kidnapping four peacekeepers of the United Nations-African Union Mission in Darfur (UNAMID), Khartoum's al-Sahafa daily reported Thursday.

Ibrahim al-Dugi, spokesperson of the People's Struggle Movement, said the abducted peacekeepers were two male and two female and they were in good health, according to the report.

He set a ransom of one billion Sudanese pounds (about 447.7 million U.S. dollars) and also demanded release of the movement's detainees held by South Darfur State's government as conditions to release the kidnapped peacekeepers, the report added.

However, UNAMID spokesperson Noureddine Mezni affirmed that the mission has not been contacted by the kidnappers.

In the meantime, a high level security delegation from UNAMID headquarters in El Fasher arrived in Nyala, capital of South Darfur State, to follow up the issue, while the mission authorities in Nyala said they have previously dealt with similar incidents, the report said.

On Tuesday, UNAMID said in a statement that four of its peacekeepers were missing since Monday evening in Nyala.

Later on the same day, an anonymous UNAMID source told Xinhua that four South African peacekeepers were stopped by some 10 gunmen when they were driving from their working site to their private accommodation near Nyala on Sunday.