Women and children rallied quietly outside Sudan's state security headquarters Thursday calling for the release of detainees held in a crackdown after protests over fuel price hikes, an AFP reporter said.
The crowd of around 45 carried photographs of the detainees, including social media activist Dalia El Roubi, the reporter said.
Children held signs reading: "Freedom for my mum".
Roubi, an employee of the World Bank in Khartoum, was taken from her home on Monday. Her husband Abdelrahman Elmahdi told AFP he had still heard no news about her by Thursday.
Sudan's government says it has arrested about 700 "criminals" after last week's protests.
But rights watchdog Amnesty International said in a statement on Wednesday that "reports from journalists, members of opposition parties, activists, and family members indicate that the figures are much higher".
It said security forces were believed to have killed more than 200 protesters, many with gunshot wounds to the head and chest.
Authorities say 34 people died after petrol and diesel prices jumped on September 23 when the government cut fuel subsidies, sending thousands into the streets in the worst urban unrest during President Omar al-Bashir's 24-year rule.
The government said it had to intervene last week when crowds turned violent, attacking petrol stations and police facilities.