Sudan's military on Tuesday cancelled a power-transfer agreement with protesters and called for elections within nine months, a day after forcefully breaking up a weeks-long sit-in, leaving more than 30 dead.
The Transitional Military Council ousted president Omar al-Bashir in April after months of protests against his authoritarian rule and had agreed a three-year transition period to a civilian administration.
But army chief General Abdel Fattah al-Burhan announced in a televised statement the plan had been ditched and an election would take place under "regional and international supervision".
"The military council decides on the following: cancelling what was agreed on and stopping negotiating with the Alliance for Freedom and Change, and to call for general elections within a period not exceeding nine months," Burhan said.
Dozens of demonstrators were killed and hundreds more wounded on Monday in the bloody crackdown outside Khartoum's army headquarters, which was met with sharp international condemnation.
Heavily armed members of the paramilitary Rapid Support Forces were deployed around the capital, guarding entrances to the bridges that cross the Nile, and moved in convoys around the city.
The United States called it a "brutal" crackdown on protesters, who want the generals behind the overthrow of veteran president Omar al-Bashir to hand over to civilian rule.
UN Secretary-General Antonio Guterres condemned the excessive use of force against protesters and called for an independent investigation.
The UN Security Council will meet behind closed doors on Tuesday to discuss Sudan, after Britain and Germany requested the talks, diplomats said.
The Central Committee of Sudanese Doctors, which is close to the protesters, said the "massacre" toll had risen to more than 30, with "hundreds of wounded".
An eight-year-old child was among those killed, it said, and called for "urgent support" from humanitarian organisations to help the wounded.
Footage from the Royal Care hospital earlier in the day near the site of the sit-in showed people on the floors of the wards receiving treatment as men in uniforms sitting in pickup trucks gathered outside.
An AFP correspondent said the streets of the capital were largely empty Monday night, a time the city is usually busy.
Some streets were blocked off by demonstrators who had erected barricades made from stones, tree trunks and burning tyres earlier in the day.
Many shops and businesses were shuttered around the city.
The military council denied its forces violently dispersed the sit-in in front of army headquarters, as demonstrators took to the streets in towns elsewhere in the country.
But protest leaders said the main site in Khartoum had been cleared.
"The Rapid Support Forces and the army and police and militia battalions dispersed the peaceful sit-in," said the Alliance for Freedom and Change.
Outside the army headquarters "there is no one, but the pure bodies of our martyrs that it has not been possible to evacuate from the site".
The Sudanese Professionals Association, which spearheaded nationwide protests that started in December, said Monday's crackdown amounted to a "bloody massacre".
It called on Sudanese to take part in "total civil disobedience" to topple the military council.
It also asked people to go out on Tuesday to hold Eid prayers to mark the end of Ramadan, "pray for the martyrs" and then "demonstrate peacefully".
The official date of Eid al-Fitr in Sudan has been fixed for Wednesday, official news agency SUNA said.
The doctors' committee said forces had opened fire inside the city's East Nile Hospital and had chased "peaceful protesters".
Rallies against Bashir's authoritarian, three-decade rule led to his ouster in April, but protesters had remained outside the army headquarters calling on the generals to cede power to a transitional authority.
Britain's ambassador to Khartoum, Irfan Siddiq, said he had heard "heavy gunfire" from his residence.
The US embassy in Khartoum said "security forces' attacks against protesters and other civilians is wrong and must stop".
"Responsibility falls on the TMC. The TMC cannot responsibly lead the people of Sudan," it added, referring to the transitional military council.
Tibor Nagy, the assistant secretary of state for Africa, tweeted that it was a "brutal and coordinated attack, led by the Rapid Support Forces militia, that mirrors some of the worst offences of the Bashir regime".
Moussa Faki, the head of the African Union Commission, urged "an immediate and transparent investigation in order to hold all those responsible accountable".
Amnesty International urged the international community to consider "all forms of peaceful pressure, including targeted sanctions on those members of the Sudanese transitional authorities responsible for this morning's violent attack on sleeping protesters".
The Alliance for Freedom and Change announced "the end of all political contact and negotiations with the putschist Council" following the deaths, even as the United Arab Emirates and Egypt appealed for the two sides to talk.