Eyewitness footage from Omdurman, across the Nile from capital Khartoum, showed protesters chanting and waving flags.
One protester was killed by live fire from security forces in Omdurman, and many others were wounded, the Central Committee of Sudanese Doctors said.
The demonstrations come two days after military leader Abdel Fattah al-Burhan announced the formation of a new ruling council that excludes the civilian coalition the military had been sharing power with since 2019.
Sudanese pro-democracy groups condemned the move and vowed to continue their campaign of civil disobedience and protests against the Oct. 25 coup.
Security forces closed bridges on Saturday between central Khartoum and its twin cities of Omdurman and Khartoum North to vehicles and pedestrians, laying barbed wire to block access. Roads to strategic sites were also shut.