Thousands of protesters marching towards Sudan's presidential palace were blocked by police firing tear gas, as an anti-military campaign entered its 10th month.
Protests have continued weekly since an Oct. 25 military takeover that halted a transition to democracy and plunged the country into turmoil.
Police on Sunday blocked protesters from reaching the kilometre-long road that leads to the presidential palace and chased them into nearby side streets, Reuters journalists said.
Military leaders have said they are prepared to step aside if civilian groups can agree on a new government but political parties have been sceptical.
However, former Sovereign Council member Mohamed al-Faki Suleiman said in an interview with local media outlet Sudan Tribune on Saturday that new constitutional arrangements were being discussed between the former ruling Forces of Freedom and Change (FFC) coalition and other "revolutionary forces".
Sunday's protests were the latest in a series of demonstrations since multi-day sit-ins in Sudan's capital prior to the Eid holiday. Last week, a protest called for by the FFC was attacked by unidentified assailants.
At least 116 people have been killed in the protests, and thousands injured, many by gunfire, according to medics.
Protesters assume they will be arrested, injured, or killed, said an injured protester, who asked to be referred to by his nickname Karika.
"We don't think we'll make it back home, and so we have only one message: the military should go to the barricades and the Rapid Support Forces should be dissolved," he said, referencing the country's powerful paramilitary group.
(Reporting by Khartoum team, writing by Nafisa Eltahir, editing by Andrew Cawthorne and Barbara Lewis)
