Sudan’s military said it has dissolved civilian government of that country, arrested political leaders and declared a state of emergency.
Gen Abdel Fattah Burhan, who had been heading a joint council with civilian leaders, blamed political infighting.
Protesters have taken to the streets of the capital, Khartoum, and there are reports of gunfire.
Military and civilian leaders have been at odds since long-time ruler Omar al-Bashir was overthrown two years ago and a transitional government set up.
Video footage from the north African nation’s capital on Monday showed protesters manning lit barricades and entering the area near the military’s headquarters.
Prime Minister Abdallah Hamdok is among those reported to have been put under house arrest, along with members of his cabinet and other civilian leaders.
A statement from the information ministry on Facebook said those arrested were being held in “an unidentified location”.
It also said Mr Hamdok was being pressed to support a coup but was refusing to do so and he urged people to continue with peaceful protests to “defend the revolution”.
Gen Burhan has been heading the Sovereign Council, part of a power-sharing arrangement between military and civilian leaders.
In a televised address, he said infighting between politicians, ambition and incitement to violence had forced him to act to protect the safety of the nation.
He said Sudan was still committed to “international accords” and the transition to civilian rule, with elections planned for July 2023.
But thousands of protesters have already taken to the streets to denounce a coup, and there has also been international condemnation of the military’s move.
The UK’s special envoy for Sudan and South Sudan, Robert Fairweather, tweeted that military arrests of civilian leaders was “a betrayal of the revolution, the transition and the Sudanese people”.
The US, UN, EU and Arab League have also expressed deep concern.
Witnesses say the internet is down and that army and paramilitary troops have been deployed across the city. Khartoum airport is now closed, and international flights are suspended.