Thousands of protesters returned to the streets to support the country's democratic transition which was derailed following a military takeover earlier this week.
Sudanese security forces have killed three people during protests against this week's military coup.
"A third protester died... from a gunshot to the chest by the putschist military council," the independent Central Committee for Sudanese Doctors said on Saturday, adding he was also killed in the city of Omdurman.
The committee earlier said in a tweet that two demonstrators were killed by the military in the same city.
It added that one was shot in the head while the other was shot in the stomach.
Thousands of Sudanese anti-coup protesters took to the streets on Saturday to support the country's democratic transition which a military takeover and deadly crackdown derailed.
The protests come almost a week after the military last Monday detained Sudan's civilian leadership, dissolved the government and declared a state of emergency, leading to a chorus of international condemnation.
The crackdown by security forces earlier left at least eleven nine protesters dead and wounded around 170.
Despite the bloodshed, organisers on Saturday aimed to stage a "million-strong" march against the military's power grab, similar to mass protests that led to the toppling of Omar al-Bashir in 2019.
'No to military rule'
Hundreds gathered in the capital Khartoum and its twin cities of Omdurman and Khartoum-North, according to witnesses.
"No, no to military rule", and "We are free revolutionaries and we will continue the road" of democratic transition, they chanted in Khartoum.
Others held posters of Prime Minister Abdalla Hamdok, ousted by the military, with slogans saying, "Don't back down."
In east Khartoum, protesters set car tyres on fire and held posters reading, "it's impossible to go back", while in the city's southern district banners expressed concern that the country might end up back on Washington's state sponsors of terrorism list.
That designation, accompanied by years of crippling sanctions, was lifted only last December which opened the way this year to more than $50 billion in debt relief and renewed largesse from the International Monetary Fund and World Bank.
After the coup, the World Bank suspended aid to Sudan.
Other protesters called for "freedom to the members of cabinet" who have been detained since the putsch.
Several pro-democracy activists have also been arrested following the takeover led by General Abdel Fattah al-Burhan, Sudan's de facto leader since the ouster of Bashir which came at the cost of more than 250 lives.
On the eve of Saturday's rallies, a US official put this week's death toll at between 20 and 30, adding the protests would be a "real test" of the intentions of Sudan's military.
"We call on the security forces to refrain from any and all violence against protesters and to fully respect the citizens' right to demonstrate peacefully," the official in Washington said on condition of anonymity.
A similar call came from Britain's special envoy for Sudan and South Sudan, Robert Fairweather.
"The security services and their leaders will bear responsibility for any violence towards any protesters," he said on Twitter.
Phone lines were largely down by Saturday morning, as security forces deployed in large numbers and blocked bridges connecting the capital, Khartoum, with its sister cities.
They set up random checkpoints on main roads, randomly frisking passers-by and searching cars.