Shells hit a United Nations base in Sudan's troubled South Kordofan state on Friday, killing one peacekeeper and wounding two more, a U.N. spokesman said.

Two shells struck a U.N. logistics base in South Kordofan's main city Kadugli, U.N. peacekeeping spokesman Kieran Dwyer told Agence France Presse. Rebels have been fighting Sudanese forces in the state for the past two years and the U.N. says there is a major humanitarian crisis there.

Egyptian President Mohammed Morsi has warned that "all options are open" in confronting an Ethiopian project to build a dam on the Blue Nile, which may diminish Egypt's water supply.

"I confirm that all options are open to deal with this subject," the Islamist president told hundreds of his supporters late Monday at a conference on the issue.

A Sudanese nurse working for an international aid agency in Sudan's troubled Darfur region has been shot dead during a gun battle inside a camp for displaced people, humanitarian workers said on Tuesday.

It is the first known death of an aid worker in Sudan since a Sudanese driver for the United Nations World Food Program was killed during an attack in war-torn South Kordofan state last August.

The Sudanese armed forces burned and shot civilians to death in a "scorched earth" campaign against a rebel chief's home district in Blue Nile state, Amnesty International said on Tuesday.

Satellite imagery confirms that the attacks in Blue Nile's Ingessana Hills, the birthplace of rebel chairman Malik Agar, occurred in the first half of last year, the London-based watchdog said in a 74-page report.

South Sudanese President Salva Kiir said Monday he would refer oil arguments with arch-rivals Sudan to African Union mediators, vowing not to take the country back to war.

"The people of South Sudan should remain calm and patient as we work with the African Union to resolve this impasse with Sudan," Kiir told reporters, while condemning the "aggressive attitude" of Khartoum.

Sudan on Sunday put on hold nine security and economic pacts with South Sudan, including on vital oil shipments, but said Khartoum remained committed to good relations if Juba ended support for rebels.

"We will stop all nine agreements, not only oil," Information Minister Ahmed Bilal Osman said at a news conference.

Sudanese President Omar al-Bashir on Saturday ordered a halt to the flow of oil from South Sudan, less than two months after southern crude began moving again, official radio said.

"Bashir ordered the minister of oil to stop the flow of South Sudanese oil from tomorrow, Sunday," Radio Omdurman reported in an SMS message which gave no further details.

Sudan's opposition alliance announced on Saturday a 100-day plan for the peaceful overthrow of President Omar al-Bashir, who has been in power for more than two decades.

"I expect the regime will fall before the 100 days finish," said Farouk Abu Issa, who represents more than 20 opposition parties.

Two Sudanese air force crew died on Thursday when their helicopter crashed in war-torn Blue Nile state, the army said, a week after another chopper went down in conflict-plagued South Kordofan.

The incident happened near the airport outside Ed Damazin, the capital of Blue Nile state, said army spokesman Sawarmi Khaled Saad.

At least 38 people died in Sudan Tuesday in one of the country's worst road accidents in years when a bus collided with a truck, police said, blaming the accident on speeding.

"Because of a crash this morning between a bus and a truck south of El Gutaina town in White Nile state, 38 people died and others were injured," a police statement said.