At least seven people were killed after security forces used gunfire and tear gas to disperse demonstrations against last year's military coup.
Sudanese security forces have killed seven protesters among thousands rallying against last year's military coup.
Three protesters "were killed by live bullets" by "militias of the putschist military council" on Monday, anti-coup medics said on the Facebook page of Khartoum state's Health Ministry.
The independent Central Committee of Sudan Doctors said four more demonstrators were killed "during a massacre by the coup authorities who were seeking to disperse the protests."
Thousands of demonstrators carrying the Sudanese flag gathered in central Khartoum as well as in Wad Madani, a city to the south.
Security officers, deployed in large numbers, fired volleys of tear gas at the Khartoum protesters heading toward the presidential palace, according to AFP news agency.
Several people were seen suffering breathing difficulties and others bleeding due to wounds by tear gas canisters, the AFP correspondent said.
Sawsan Salah, from the capital's twin city of Omdurman, said protesters burnt car tyres and carried photos of people killed during other demonstrations since the October 25 coup.
In Wad Madani, "around 2,000 people took to the streets as they called for civilian rule", said Emad Mohammed, a witness there.
Protesters — sometimes numbering in the tens of thousands — have regularly taken to the streets despite a deadly security clampdown.
The latest killings bring the death toll to 71 of protesters killed since the October 25 coup led by General Abdel Fattah al Burhan.
US diplomatic push
The latest rallies came as US envoy to the Horn of Africa David Satterfield and Assistant Secretary of State for African Affairs Molly Phee are expected in Khartoum this week to push a message of "justice" for the Sudanese.
And last week, the United Nations said it will launch talks involving political, military and social actors to help resolve the crisis.
Sudan's military takeover triggered wide international condemnation and derailed a fragile transition to civilian rule following the April 2019 ouster of longtime autocratic president Omar al Bashir.
On Thursday, Sudanese authorities said protesters stabbed to death a police general, the first fatality among security forces.
Authorities have repeatedly denied using live ammunition in confronting demonstrators and insist scores of security personnel have been wounded during protests that have often "deviated from peacefulness".
Earlier this month, Sudan's civilian prime minister Abdalla Hamdok resigned saying the country was now at a "dangerous crossroads threatening its very survival".