U.S. Secretary of State John Kerry Saturday accused Sudanese President Omar al-Bashir of repressing the people of the South Kordofan and Blue Nile regions and trying to impose Islamic rule on them.

In both regions "you have people who for a long time have felt that they want their secular governance and identity respected," Kerry told reporters on the sidelines of an African Union summit.

A resurgence of fighting in Sudan's western Darfur region has driven 300,000 people from their homes so far this year, U.N. humanitarian aid chief Valerie Amos said on Thursday.

She was speaking at the end of a three-day visit to Sudan during which she visited a camp for displaced people in Darfur.

At least 29 people were killed when cattle raiders from a South Sudanese minority group opened fire on members of another minority in a village in Upper Nile state, a local official said Sunday.

The gunmen crept into Tolleri village in Ulang county in the early hours of Saturday morning and sprayed it with bullets, killing 23 people instantly, said Dak Tap Chuol, commissioner for the nearby town of Nasir.

Two Darfur rebel chiefs who signed an accord with the Sudanese government have been killed in an insurgent attack near the strife-torn region's border with Chad, the foreign ministry said on Monday.

"The forces of the Revolutionary Front carried out an odious terrorist operation on Sunday, murdering in cold blood the two leaders Mohammed Bashar and Arko Dahiya" who "were on a peaceful mission in the Yamna region on the border with Chad," it said in a statement.

South Sudanese President Salva Kiir has spoken with his Sudanese counterpart Omar al-Bashir in a bid to ease tensions after deadly clashes in Abyei, a region claimed by both sides, officials said Monday.

U.N. chief Ban Ki-moon and the African Union have appealed for calm in the flashpoint area after the killing of a tribal chief and a U.N. peacekeeper on Saturday.

An Ethiopian peacekeeper was killed and two wounded in an ambush on a convoy in which a top tribal leader was killed in the disputed Abyei region between Sudan and South Sudan, the United Nations said late Saturday.

U.N. leader Ban Ki-moon said he "strongly condemns" the killings, but called for efforts to prevent an escalation between the rival countries.

At least 80 people have been killed in the latest outbreak of fighting between Arab groups in western Sudan's Darfur region, tribal leaders said on Friday.

"Fighting was going on until last night and from our side we have 37 dead," said Ibrahim al-Sheikh, a leader of the Beni Halba tribe.

Around 100 miners are estimated to have died inside a collapsed gold mine in Sudan's Darfur region and nine rescuers trying to free them are now trapped, a miner said on Friday.

"Nine of the rescue team disappeared when the land collapsed around them yesterday (Thursday)," said the miner, who had visited the scene and asked to remain anonymous.

Dozens of people have been killed in a gold mine collapse in Sudan's Darfur region, said the chief of the district where fighting over gold in January led to the region's worst unrest in years.

"The number of people who died is more than 60," Haroun al-Hassan, the local commissioner in Jebel Amir, North Darfur, said on Thursday.

President Omar al-Bashir has pardoned six members of Sudan's powerful security service just days after they were jailed over a coup attempt last year, state-linked media said on Tuesday.

Several army officers convicted this month for the same plot have also been released under a presidential pardon.