The African Union has suspended Sudan until there is civilian rule, intensifying global pressure on its new military leaders to stand down after the worst violence since Omar al-Bashir's fall in April.
However, Ethiopia - where the continental bloc is based - planned a mediation effort, with Prime Minister Abiy Ahmed due on Friday to meet members of both the ruling Transitional Council and the opposition, a diplomatic source said.
Both sides had been in talks over a civilian-led transition to democracy. But their already faltering negotiations collapsed when security forces stormed a sit-in protest camp on Monday, killing dozens of people.
Meeting in Ethiopia's capital Addis Ababa, the AU's peace and security council invoked its response to interruptions of constitutional rule by suspending Sudan.
That followed widespread condemnation of the bloodshed from the United Nations and the West.
Former colonial ruler Britain summoned Sudan's ambassador to the Foreign Office to express its concerns.
The Declaration of Freedom and Change Forces opposition alliance said it was not ready for more dialogue and demanded that the military hand over power.
"The coup council and anyone involved in its crimes since April 11 must be held accountable," it added in a statement, also demanding dissolution of the feared paramilitary body the Rapid Support Forces that has led crackdowns.
The opposition says 108 people died in Monday's violence, but Sudan's Health Ministry put the toll at 61.
The RSF, led by the military council's deputy leader General Mohamed Hamdan Dagalo, emerged from militias that fought insurgents in western Darfur region since 2003.
The militias are accused of atrocities in Darfur, and Bashir was indicted by the International Criminal Court for war crimes and genocide - which he denies. He is now detained in Khartoum.
