Sudan’s security forces have fired tear gas to disperse protesters demanding an end to military rule.
One protester was also reportedly killed as tens of thousands rallied across Sudan to push the junta to hand power to a civilian-led administration.
The protests are the biggest since dozens were killed in a crackdown on pro-democracy activists on 3 June.
Sudan has been in turmoil since the military ousted President Omar al-Bashir in April.
It followed a popular uprising against his rule.
Mr Bashir seized power in a coup on 30 June 1989.
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On Sunday, protesters defied the heavy presence of troops, including the feared paramilitary Rapid Security Forces (RSF), to take part in what organisers had billed a “million-strong” march.
“We are here for the martyrs of the [June 3] sit-in. We want a civilian state that guarantees our freedom. We want to get rid of military dictatorship,” a 23-year-old protester named only as Zeinab told AFP news agency.
Security forces fired tear gas to disperse demonstrators near the presidential palace and three other districts in the capital, Khartoum, AFP reports.
Tear gas was also fired in Khartoum’s twin city of Omdurman and the eastern town of Gadaref.
In Atbara city in the north-east, a young protester died of a bullet wound to the chest, the pro-opposition Central Committee of Sudan Doctors said.
‘Massive show of strength’
By Mohanad Hashim, BBC Sudan analyst
If the military thought it could scare protesters, it was wrong. The protests are a massive show of strength by the pro-democracy movement.
It has pulled off the biggest demonstration since the junta took power, despite an internet blackout and the security forces blocking bridges to prevent people from joining marches.
Some are saying that hundreds of thousands rallied across Sudan, more than the number who took to the streets before Omar al-Bashir was ousted by his former allies in the military. The junta is clearly on the back foot – and has said it is prepared to resume talks with the opposition.
But many wonder whether it can be trusted.
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On Saturday, paramilitary forces broke up a news conference called by the Sudanese Professionals Association (SPA), one of the main organisers of the protest.
The military said it would hold the opposition responsible for any violence or loss of life in the protests.
Gen Mohamed Hamdan Dagalo, also known as Hemeti, warned of “vandals” and a “concealed agenda” that might take advantage of the demonstrations.
Talks between the Transitional Military Council (TMC) and the opposition collapsed after the 3 June crackdown, when the RSF violent suppressed protests in Khartoum.
They have not resumed despite mediation by the African Union (AU) and Ethiopian Prime Minister Abiy Ahmed.
On Friday, the SPA said two leading members of the opposition had been detained and urged “the international community to demand their immediate release”.