Hundreds of activists massed Friday near the presidential palace in the capital Khartoum, after at least nine people were killed during Thursday's rallies against a military takeover led by army chief Abdel Fattah al-Burhan last October.
"Down with Burhan," some protesters chanted while others, carrying photos of people killed in months of protest-related violence, yelled: "We call for retribution!"
The activists demand the restoration of the transition to civilian rule, that was launched shortly after the 2019 ouster of veteran president Omar al-Bashir but which has been derailed since.
The US State Department's Bureau for African Affairs stated on Twitter "Tens of Thousands of Sudanese took to the street today to demand democracy. We support their aspirations."
"We condemn in the strongest terms the use of live fire by security forces against civilians. We offer our condolences to those who lost family members."
The "violence needs to end," demanded UN special representative Volker Perthes.
The death toll from protest-related violence has reached 113 since the coup, with the latest fatality reported Friday after a demonstrator died from wounds sustained at a June 24 rally, according to pro-democracy medics.
Sudan's police meanwhile accused protesters of wounding 96 police and 129 military officers, "some critically", on Thursday, as well as damaging vehicles and starting fires.