Sudanese forces opened fire on demonstrators Monday, killing seven people, making it one of the bloodiest in a string of protests following a military coup in October.
The violence comes ahead of a visit by US diplomats who will attempt to broker an end to the months-long crisis in the country.
Security forces fired tear gas as they blocked thousands of protesters from advancing on the presidential palace in the capital, Khartoum, on Monday.
Demonstrations also turned violent in the suburb of North Khartoum and the city of Omdurman across the Nile
The Central Committee of Sudanese Doctors, a group of medics aligned with the protest movement, said security forces used ammunition and stun grenades.
Government sources put the death toll at three, though UN special representative Volker Perthes confirmed at least seven people were killed and "scores injured".
The head of the UN Integrated transition Assistance mission Sudan (UNITAMS) condemned the "continued use of live ammunition" to put down the protests.
Sudanese authorities have repeatedly denied using live ammunition against demonstrations.
UN calls for restraint
Nine UN Security Council members, including Britain and France, urged all parties in Sudan to "refrain from the use of violence", stressing the importance of "peaceful assembly and freedom of expression".
Medics say at least 71 people have been killed by security forces since the army took over on 25 October.
Since the coup, protesters have regularly taken to the streets to demand civilian rule, despite the security clampdown and periodic cuts to communications since the coup lead by General Abdel Fattah al-Burhan.
Burhan held an emergency meeting on Monday with security chiefs who blamed the "chaos" on protesters who "deviated from legitimate peaceful demonstration".
Protest organisers announced two days of strikes and civil disobedience following what they called a “massacre”.
The military power grab derailed a fragile transition to civilian rule following the April 2019 ouster of president Omar al-Bashir.
US to try to mediate
The US envoy to the Horn of Africa David Satterfield and Assistant Secretary of State for African Affairs Molly Phee are expected in Sudan in coming days, in a bid to "facilitate a renewed civilian-led transition to democracy", the US State Department said.
Washington's push comes after the United Nations said last week it will launch talks involving key figures to help resolve the crisis.
(With wires)
