The reports, which came days after a wave of government bombings on rebel positions in South Darfur, underlined the ongoing turmoil in the region in the face of troubled peace efforts.

The new wave of violence, which ended a period of relative calm in the remote western region, also raised tensions ahead of a decision by the International Criminal Court on whether to issue an arrest warrant against Sudan's President for alleged war crimes in Darfur.

International experts say more than six years of fighting in Darfur has killed 200,000 and driven 2.5 million from their homes. Khartoum accuses the western media of exaggerating the conflict.

Government forces in the area of Girayda in South Darfur opened fire on a convoy of fighters on Thursday afternoon, said the spokesman for the joint UN/African Union UNAMID peacekeeping force in Darfur.

UNAMID spokesman Noureddine Mezni said the fighters had recently joined Darfur's rebel Justice and Equality Movement (JEM).

JEM denied their men were involved in the clash, telling Reuters the fighters were loyal to Minni Arcua Minnawi, the only rebel leader to sign a peace deal with the government in 2006.

"The army didn't know that these were Minni forces, they thought they were JEM," said the chairman of JEM's legislative council Dr Al-Tahir al-Feki.

"Three of their vehicles were destroyed and one senior Minnawi commander was killed."

No one was immediately available to comment on the reports from Sudan's armed forces or Minnawi's movement.

UNAMID confirmed JEM seized control of the south Darfur town of Muhajiriya last week, taking it from forces loyal to Minnawi. Days earlier, Sudan's government said it bombed JEM positions around Muhajiriya.