Sudanese security forces have fired tear gas and live ammunition to disperse protesters setting up barricades in Khartoum.
Four people have been killed on the first day of a strike, according to doctors aligned to the opposition.
Campaigners have called for ongoing civil disobedience from Sunday to make it as difficult as possible for the military to govern Sudan.
It comes days after a military crackdown left dozens dead.
A number of Sudan’s bank, airport and electricity workers were arrested ahead of the strike against the military rule, the main protest group said.
The Sudanese Professionals Association (SPA) said employees were also being threatened by the authorities to scare them into going to work instead of taking part in the nationwide strike.