Saudi Arabia denied permission for a plane carrying Sudanese President Omar al-Bashir to cross its airspace on Sunday for the swearing-in of Iran's new president, Khartoum said.

The aircraft had to turn back.

A new outbreak of tribal violence in Sudan's Darfur region has killed nine people, official media said on Saturday, in fighting that has added to worsening insecurity in the region.

The deaths occurred during two days of unrest involving Arabs and the non-Arab Fur tribe in Kebkabiya, North Darfur, the SUNA news agency reported.

A convoy attacked by rebels who killed nine soldiers in Sudan's Kordofan region was carrying fuel for an international peacekeeping mission, the foreign ministry said.

The convoy was transporting fuel for the United Nations Interim Security Force for Abyei (UNISFA), the foreign ministry said in a statement received late on Wednesday.

Warring Arab tribes in Sudan's Darfur region said on Wednesday that they had reached a tentative ceasefire, after fighting which one of them said had killed more than 200 people.

"Last night we reached an agreement to calm things down," Ahmed Khiri, a Misseriya tribal leader, told Agence France Presse.

The U.N. Security Council on Tuesday called for a review of the U.N.-African Union peacekeeping mission in Darfur which has faced mounting deadly attacks.

Seven Tanzanian peacekeepers were killed this month in the latest ambush on the force. But the Security Council is also concerned at the failure of attempts to negotiate an end to the decade old conflict in the western Sudanese region.

Fighting between rival Arab tribes in Sudan's Darfur region spread on Monday, after clashes last week left scores dead, a leader of one of the tribes said.

"This morning there was fighting in the Garsila area. It's still going on," said Ahmed Khiri, a Misseriya tribal chief.

Fighting in the past two days between rival tribes in Sudan's Darfur region has killed 94 people, despite a peace deal between them, a tribal leader said on Saturday.

"Since yesterday there has been a clash between us and the Salamat after they tried to attack us," Ahmed Khiri, who described himself as a leader of fighters from the Misseriya tribe, told Agence France Presse.

Sudanese rebels clashed with government forces on Saturday for the second time this week in the strategic South-North Kordofan region, the insurgents said.

The Justice and Equality Movement (JEM), a Darfur-based group which is part of a wider rebel alliance seeking to topple the government, said it ambushed a convoy north of Dilling town.

South Sudan must move quickly to form a new government or risk even greater instability, a top U.S. official said after the country's president fired his whole cabinet.

President Salva Kiir, leader of the world's newest nation, was holding talks Thursday aimed at setting up a new government two days after sacking his entire team in a sign of the political in-fighting in Juba.

Sudanese rebels said they attacked government forces in North Kordofan on Wednesday, days before a Khartoum deadline to halt South Sudan's oil exports over allegations it is backing the insurgents.

The Justice and Equality Movement, a Darfur-based group which is part of a wider rebel alliance, said it attacked a military convoy at Sidrah, about 30 kilometers (20 miles) south of El Rahad town.