At least 14 people were wounded when Sudanese forces tried to remove demonstrators from central Khartoum on Wednesday, according to the opposition-linked group the Sudanese Professionals' Association (SPA).
An injured man was filmed being carried on a stretcher to a waiting ambulance, much to the apparent fury of the crowd.
The SPA blamed the Rapid Support Forces, the Sudanese military's paramilitary wing, for the violence after they forcibly tried to remove barricades in the city centre.
Later, Sudan's Transitional Military Council (TMC) suspended talks with opposition leaders on the installation of civilian rule for at least 72 hours. Lieutenant General Abdel Fattah al-Burhan accused demonstrators of breaking an understanding on the de-escalation process and causing disruption to the capital.
The two sides, which disagree on the transfer of power to civilian rule and the extent of the military's role in it, had reportedly agreed to a three-year transition period earlier in the day.