President Omar al-Bashir, who ruled Sudan in autocratic style for 30 years, was overthrown and arrested in a coup by the armed forces on Thursday, but protesters took to the streets demanding the military hand over power to civilians.
The ouster of Bashir, 75, followed months of demonstrations against his rule.
In an address on state television, Defense Minister Awad Mohamed Ahmed Ibn Auf, announced a two-year period of military rule to be followed by presidential elections.
He said Bashir was being detained in a "safe place" and a military council would now run the country. He did not say who would head it.
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Ibn Auf announced a state of emergency, a nationwide ceasefire and the suspension of the constitution. Seated on a gold-upholstered armchair, he said Sudan's airspace would be closed for 24 hours and border crossings shut until further notice.
The main organizer of protests against Bashir, the Sudanese Professionals Association (SPA), rejected the minister's plans. It called on protesters to maintain a sit-in outside the defense ministry that began on Saturday.
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Shortly afterwards, thousands of demonstrators packed the streets of central Khartoum, their mood turning from jubilation at Bashir's expected departure to anger at the announcement of a military-led transition, a Reuters witness said.
"Fall, again!" many chanted, adapting an earlier anti-Bashir slogan of "Fall, that's all!".
Sudanese sources told Reuters that Bashir was at the presidential residence under "heavy guard". A son of Sadiq al-Mahdi, the head of the main opposition Umma Party, told al-Hadath TV that Bashir was being held with "a number of leaders of the terrorist Muslim Brotherhood group".
Bashir has been indicted by the International Criminal Court in The Hague and is facing an arrest warrant over allegations of genocide in Sudan's Darfur region during an insurgency that began in 2003 and led to death of an estimated 300,000 people.
Despite the arrest warrant Bashir defied the court by visiting several ICC member states. Diplomatic rows broke out when he went to South Africa in 2015 and Jordan in 2017 and both failed to arrest him.
The downfall of Bashir follows the toppling this month of Algerian strongman Abdelaziz Bouteflika, also following mass protests after two decades in power.
Military rule again?
Names of Bashir's possible successors that have been circulating include the defense minister, an ex-military intelligence chief, also an Islamist, and former army chief of staff Emad al-Din Adawi.
Adawi is said to be favoured by regional neighbours at odds with Bashir over his Islamist leanings.
Omar Saleh Sennar, a senior SPA member, said the group expected to negotiate with the military over a transfer of power.
"We will only accept a transitional civilian government," Sennar told Reuters.
Kamal Omar, 38, another demonstrator, said: "We will continue our sit-in until we prevail".
Ibn Auf announced the release of all political prisoners, and images circulated of freed detainees joining the protests.
Troops were deployed in strategic areas of the capital and also stormed the headquarters of Bashir's Islamic Movement, the main component of the ruling National Congress Party.
In the eastern cities of Port Sudan and Kassala, protesters attacked the offices of Sudan's intelligence and security service, witnesses said.
Bashir, a former paratrooper who seized power in a bloodless coup in 1989, has been a divisive figure who has managed his way through one internal crisis after another while withstanding attempts by the West to weaken him.
Sudan has suffered prolonged periods of isolation since 1993, when the United States added Bashir's government to its list of terrorism sponsors for harbouring Islamist militants. Washington followed up with sanctions four years later.
A long civil war with southern separatists ended in 2005 and South Sudan became an independent country in 2011.
Since December, Sudan has been rocked by persistent protests sparked by the government's attempt to raise the price of bread, and an economic crisis that has led to fuel and cash shortages.
The unrest escalated since the weekend, when thousands of demonstrators began camping out outside the defense ministry compound, where Bashir's residence is located.
Clashes erupted between soldiers trying to protect the protesters and intelligence and security personnel trying to disperse them. Around 20 people were killed since the sit-in began.
Activists abroad pressed for Sudan to turn over Bashir to the International Criminal Court.
"Victims of the gravest crimes in Darfur should not have to wait any longer for justice" said Jehanne Henry, associate director at the Africa division of Human Rights Watch.
Months of protest
The months of protests have plunged Sudan into its worst crisis in years. The demonstrations initially erupted last December with rallies against a spiraling economy, but quickly escalated into calls for an end to embattled al-Bashir's rule.
Security forces have responded to the protest movement with a fierce crackdown, killing dozens. Al-Bashir banned unauthorized public gatherings and granted sweeping powers to the police since imposing a state of emergency last month. Security forces have used tear gas, rubber bullets, live ammunition and batons against demonstrators
The protests gained momentum last week after Algeria's President Abdelaziz Bouteflika, in power for 20 years, resigned in response to weeks of similar protests.
On Saturday, marches in Khartoum marked the 34th anniversary of the overthrow of former President al-Nimeiri in a bloodless coup. It was one of the largest turnouts in the current wave of unrest.
The military removed Nimeiri after a popular uprising in 1985. It quickly handed over power to an elected government. The dysfunctional administration lasted only a few years until al-Bashir — a career army officer — allied with Islamist hard-liners and toppled it in a coup in 1989.
Since the current protests began December 19, the military has stated its support for the country's "leadership" and pledged to protect the people's "achievements" — without mentioning al-Bashir by name.
Army troops have deployed to protect vital state installations but have not tried to stop protests and, in some cases, appeared to offer a measure of protection for the demonstrators.
All that raised the possibility that what was playing out in Khartoum on Thursday was a military takeover and removal of al-Bashir.