Sudan has rejected a U.S. request to send special forces to protect its embassy in Khartoum following violent protests against an American-made film mocking Islam, the official SUNA news agency said.

"The U.S. government has expressed its wish to send special forces to protect its embassy in Khartoum after the events that took place in most Muslim countries," SUNA quoted a foreign ministry spokesman as saying.

At least 10 soldiers were killed and another 50 were reported missing after friendly fire caused a South Sudanese military boat to sink on the Nile river, the army said Saturday.

"It was an accident. The boat was traveling at night and passed before a (control) post at Lul, which tried to stop the boat. When it did not stop they fired at the boat and it sank," army spokesman Philip Aguer told Agence France Presse, adding that there were about 170 soldiers on board.

A second protester was found dead outside the U.S. embassy in Sudan on Friday, his clothing soaked in blood, an Agence France Presse journalist said after a demonstrator was killed earlier when he was hit by a police vehicle.

The body was found at the foot of the compound's outer wall, but it was not immediately clear how he had died, the reporter said.

Hundreds of protesters upset over a movie mocking Islam demonstrated outside the American embassy in Sudan on Wednesday, an embassy official said, after attacks on U.S. missions in Libya and Egypt.

"I do believe it was a few hundred," the official said, asking for anonymity. "Our compound was not breached."

Russian experts will examine the "black box" which could hold clues as to why an Antonov aircraft crashed in Sudan killing all 32 politicians, generals and others aboard, a civil aviation official said on Monday.

"We are preparing to send the black box," to Russia, Abdelhafiz Abdelrahim, spokesman for the Sudan Civil Aviation Authority, told Agence France Presse.

Sustained fighting in Sudan's South Kordofan state has killed several dozen government troops and five rebels, the insurgents claimed on Sunday after the army said it repulsed them.

The Sudan People's Liberation Movement-North (SPLM-N) said "fighting is still continuing inside Al Moreib," a village in Rashad district of northeastern South Kordofan.

The U.N.'s refugee agency said Friday it was 'alarmed' by the state of health of large numbers of refugees in South Sudan who have fallen ill from a cold spell of weather.

A statement from the United Nations High Commissioner for Refugees (UNCHCR) said: "With 170,000 Sudanese refugees now in camps and settlements across South Sudan's Unity and Upper Niles states, the health situation among this population has become a matter of increasing alarm to us.

Powerful South Sudanese military commander Paulino Matip, a longtime rebel warlord turned army chief, has died in hospital in Kenya, officials said Wednesday.

"We have lost a champion of peace and reconciliation -- we will miss him," South Sudanese Information Minister Barnaba Marial Benjamin told Agence France Presse. "He was undergoing treatment in Nairobi. He was ill for a long time."

A Sudanese cabinet minister was among 31 people killed Sunday when an airplane crashed as it carried a delegation to war-torn South Kordofan state for Muslim Eid holiday celebrations, officials and state media said.

"All people on board were killed," Abdelhafiz Abdelrahim, spokesman for the Sudan Aviation Authority, told Agence France Presse.

A U.S. resident was re-arrested in Sudan on Monday shortly after a judge ordered him to be freed after paying a fine for his role in Arab Spring-style protests, one of his lawyers said.

Judge Abaas al-Khalifa sentenced Rudwan Daoud to the several weeks he has already spent in custody but dismissed a terrorism-linked conspiracy and other charges.