The protesters, marching in neighbourhoods across the capital and its twin cities of Bahri and Omdurman, demanded a full handover to civilian authorities and for the leaders of the Oct. 25 coup to be tried in court.
Security forces fired live bullets and tear gas after mobile phone communications were cut earlier in the day, witnesses said.
“The coup forces used live bullets heavily in different areas of the capital and there are tens of gunshot injuries, some of them in serious condition,” said the Central Committee of Sudanese Doctors, a group of medics aligned with the protest movement.
It reported 10 deaths, including seven in Bahri.
On one main road in Khartoum, protesters burned tyres and chanted: “The people are stronger, and retreat is impossible.”
Others carried pictures of people killed in previous protests and of Abdalla Hamdok, the civilian prime minister who was placed under house arrest during the coup, with the slogan: “Legitimacy comes from the street, not from the cannons.”
Images of protests in towns and cities including Port Sudan, Kassala, Dongola, Wad Madani and Geneina were posted on social media.
Security forces were heavily deployed on main roads and intersections, using tear gas to prevent gatherings, witnesses said. Bridges across the River Nile were closed.
There was no immediate comment from security forces. Military leader Abdel Fattah al-Burhan has previously said peaceful protests are allowed and that the military does not kill protesters.
The coup ended a transitional partnership between the military and a civilian coalition that helped topple autocrat Omar al-Bashir in 2019.
Despite pressure from Western states which have suspended economic assistance, efforts at mediation have stalled, with Burhan moving to cement control with help from Bashir-era veterans.
Mobile internet services in Sudan have been suspended since the coup. This has complicated a campaign of anti-military rallies, strikes and civil disobedience.
The Sudanese Congress Party, which was part of the military and civilian coalition, said one of its leaders had been arrested following a raid on his house.
On Saturday, hundreds of thousands turned out across the country to protest against the coup. Medics said seven people were killed by security forces.
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