US and African Union diplomats stepped up efforts on Thursday to find a peaceful solution to a standoff between Sudan's protesters and generals following a deadly crackdown on demonstrators.

The latest diplomatic push came as Sudanese prosecutors charged ousted leader Omar al-Bashir with corruption, two months after he was toppled by the army following nationwide protests against his rule.

The impasse between Sudan's protesters and ruling military council saw demonstrators stage a nationwide civil disobedience campaign following a crackdown against a protest camp on June 3 that left dozens dead.

The demonstrators, who are calling for a transition to civilian rule, ended the campaign on Tuesday and agreed to resume talks with the generals.

Traffic jams have returned to downtown Khartoum and some shops in the capital's famous gold market began to reopen on Thursday as more residents and office employees ventured out.

Fewer troops and members of the feared paramilitary Rapid Support Forces, accused by protesters and rights groups of leading the crackdown, were on the streets in downtown Khartoum.

But they were deployed in force in the northern district of Bahari, a bastion of protests against the military council.

"Today is my first day to work after the campaign ended but I'm not in the mood to work," said Suheir Hassan, an employee at a government office.

"On my way I passed by the sit-in area and remembered that all those voices who used to chant revolutionary slogans have now disappeared."

Protesters ended their civil disobedience campaign late on Tuesday and agreed to hold fresh talks with the ruling generals following mediation led by Ethiopian Prime Minister Abiy Ahmed.

Demonstrators launched the strike after men in military fatigues carried out their deadly assault against a sit-in of thousands of people outside the army headquarters last week.

Washington's newly appointed special envoy to Sudan, Donald Booth, along with US Assistant Secretary of State for Africa Tibor Nagy, met military council chief General Abdel Fattah al-Burhan on Thursday.

Burhan told the US envoys that Sudan and its people had a positive view of US efforts to reach a political settlement, according to a statement released by the military council.

Washington said Booth had been named to help craft a "peaceful solution" to the crisis that has rocked the northeast African country.

The Alliance for Freedom and Change umbrella protest movement said its leaders had briefed the two US officials on Wednesday on the need for a transparent investigation into the June 3 killings.

They also called for the withdrawal of "militias" from the streets in Khartoum and other towns, the lifting of an internet blockade and the establishment of a civilian administration, it said in a statement.

The AU, which suspended Sudan following the crackdown, said global efforts were being made to resolve the crisis.

"I can say without excess optimism that the discussions that we are holding with each side separately are moving forward to a great extent," AU Special Envoy to Sudan Mohamed El Hacen Lebatt told reporters on Thursday.

An international team of diplomats was working to resolve the crisis, he added.

The US diplomats were also expected to meet with top envoys from Saudi Arabia, the United Arab Emirates and Egypt in Khartoum.

Experts say the three regional Arab nations appear to back the generals.

The country's worsening economic crisis was one initial trigger for protests against Bashir's three-decade rule.

Thursday, prosecutors charged him with corruption and "possessing foreign funds, acquiring suspect and illegal wealth" and putting in place a state of emergency, state media reported.

Last month, Sudan's public prosecutor ordered the questioning of Bashir, who is being held in Khartoum's Kober prison, over money-laundering and "financing terrorism".

Talks between the protest leaders and generals collapsed in mid-May over the question of who should lead a new governing body - a civilian or a soldier.

Relations worsened following the crackdown, with protest leaders now insisting any agreement reached with the generals must be backed by "regional and international" guarantees.

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