Soldiers have arrested members of Sudan's cabinet in what the information ministry calls a military coup, prompting opponents of the takeover to take to the streets, where there have been reports of gunfire and injuries.
Prime Minister Abdalla Hamdok was detained and moved to an undisclosed location after refusing to issue a statement in support of the coup, said the information ministry, still apparently under the control of Hamdok's supporters.
It said tens of thousands of people opposed to the coup had taken to the streets and had faced gunfire near the military's headquarters in the capital Khartoum.
Sudan's state television said Abdel Fattah al-Burhan, the military officer who heads a power-sharing ruling council, was set to deliver a statement.
The director of Hamdok's office, Adam Hereika, told Dubai-based al-Arabiya TV that the military had mounted its takeover despite an agreement Hamdok had reached with Burhan, in the presence of a visiting US special envoy, Jeffrey Feltman.
Hereika accused the military of fomenting unrest in eastern Sudan and using the crisis to implement a coup.
A Reuters journalist in Khartoum saw joint forces from the military and from the powerful, paramilitary Rapid Support Forces stationed in the streets of Khartoum. They restricted civilians' movements, as protesters carrying the national flag burnt tyres in different parts of the city.
Protesters opposing the army takeover moved past barricades and entered the street surrounding military headquarters in Khartoum, footage on the Qatar-based Al-Jazeera Mubasher television channel showed.
Citing witnesses, Al-Arabiya television said there were injuries in clashes in front of army headquarters.
Sudan has been on edge since a failed coup plot last month unleashed recriminations between military and civilian groups, who have been sharing power following the toppling of long-serving ruler Omar al-Bashir two years ago.
The political transition, which was agreed after Bashir was brought down by street protests, has seen Sudan emerge from international isolation under Bashir's nearly three-decade rule.
Elections were to be held by the end of 2023.
The information ministry said military forces had arrested civilian members of the Sovereign Council and members of the government.
In a statement sent to Reuters, the ministry asked Sudanese "to block the military's movements to block the democratic transition".
"We raise our voices loudly to reject this coup attempt," it said.
The military was meant to pass leadership of the joint Sovereign Council to a civilian figure in the coming months. But transitional authorities had struggled to move forward on issues including whether to hand Bashir over to the International Criminal Court, where he is wanted for war crimes.
Feltman, the US special envoy who was visiting Sudan on the weekend, said the US was deeply alarmed at reports of a military takeover.
He warned it would contravene Sudan's Constitutional Declaration and put at risk US assistance.
The UN was deeply concerned about reports of a coup and attempts to undermine Sudan's political transition, said Volker Perthes, special representative of the UN secretary general for the country.
The Arab League also expressed concern and called on all parties to adhere to an agreement about a transition to democracy.
Military forces stormed Sudanese Radio and Television headquarters in Omdurman, the twin city of Khartoum, and arrested employees, the information ministry said on its Facebook page.
The internet appeared to be down in Khartoum and Al-Arabiya reported the airport was shut and international flights suspended.
Hamdok is an economist and former senior UN official who was appointed as a technocratic prime minister in 2019 and is well respected internationally.
Though popular with pro-democracy civilian groups, he has struggled to keep the transition going due to political splits between the military and civilians and the pressures of an economic crisis.
Australian Associated Press