Protesters are rejecting a government austerity plan that slashed subsidies and doubled the price of fuel and food. But they also appear to be inspired by Arab uprisings in neighboring Egypt and Libya and are demanding the ouster of longtime Sudanese President Omar al-Bashir.
Gatherings have been quickly broken up by troops using tear gas, activists say, and in a new development, police have raided homes of the opposition.
Sudan's Ummah party said in a text message that at least three members were detained.
Siddique Tawer, of the Sudanese Baath party, said the party's spokesman Mohammed Diaa Eddin was arrested at his home early Saturday.
The arrest raids and new police directives are a sign of nervousness, Tawer said. "They are afraid of street action. They are trying to terrorize people," he said by telephone from al-Ubbayid, provincial capital of Northern Kordofan to the southwest. "They can't stop these protests. They are legitimate, against the government's economic policies, corruption, and repression of freedoms."
In al-Ubbayid, a small number of university students demonstrated outside their campus on Saturday and were joined by passers-by, he said. Police fired gas canisters to break up the protests.
State-run radio had said earlier that 150 protesters attacked a group of police officers overnight, damaging a police vehicle and forcing the police to use tear gas.
A spokesman for Sudan's ruling National Congress Party, Badr Eddin Ahmed Ibrahim, dismissed the protests, saying they were largely led by university students and were used by opposition parties to agitate against the government.
"The opposition parties have no specific goals," he said, according to comments published by the semi-official Sudan Media Center website.