Sudan’s military leaders say they are scrapping all existing agreements with the main opposition coalition and will hold elections within nine months.
The announcement came as the military faced mounting international condemnation for their violent attack on protesters in the capital, Khartoum, which reportedly left at least 30 dead.
The US said it was a “brutal attack”.
The crackdown came after the military and protesters agreed a three-year transition period to civilian rule.
Demonstrators argue that former regime of President Omar al-Bashir, who was overthrown by the military in April after months of protests, is so deeply entrenched that a transition of at least three years is needed to dismantle his political network and allow fair elections.
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The Transitional Military Council (TMC), which has governed since the coup, and negotiators for the pro-democracy movement had also agreed on the structure of a new administration.
But the TMC’s head, General Abdel Fattah al-Burhan, said in a statement broadcast on state television that they had decided to “stop negotiating with the Alliance for Freedom and Change and cancel what had been agreed on”.
An election in nine months’ time would take place under “regional and international supervision”, he added.
Speaking on BBC’s Newsday, analyst and former British ambassador to Sudan Rosalind Marsden said the snap election would “simply pave the way for much of the old regime to come back into power”.
“There’s a real risk of violence continuing,” she said.
In the wake of killings, the leaders of the pro-democracy movement said they were cutting all contact with the TMC and called for “total civil disobedience” and a general strike.