Large crowds have remained on the streets of Sudan's capital, Khartoum, through the night, ignoring a curfew declared by the military.
Long-time President Omar al-Bashir was overthrown and arrested on Thursday after months of street protests.
But demonstrators say the military council which has taken power is part of the same regime.
The fresh stand-off has raised fears of a violent confrontation between protesters and the army.
There is also a real danger that different elements of the security forces and militia could turn their guns on each other, says BBC World Service Africa editor Will Ross.
The UN and the African Union have both called for calm.