Leaders of the protests in the Sudanese capital Khartoum have called on supporters to stay in the streets two days after the military coup.
They are demanding an immediate move to civilian rule after the army ousted long-time leader Omar al-Bashir, putting him in custody.
The military wants to hold power for two years, followed by elections.
It replaced its own leader in an apparent concession to the protesters but the change did not sway them.
"We call on the armed forces to ensure the immediate transfer of power to a transitional civilian government," the Sudan Professionals Association (SPA), which has been spearheading the demonstrations, said on Facebook.
A growing economic crisis has gripped the country since the oil-rich southern part split away in 2011, and Thursday's coup followed months of unrest over the cost of living.