The head of Sudan's opposition political alliance told AFP on Thursday he had been detained by Sudanese state security agents after he spoke in support of four dead Darfuri students.
The youths' deaths, following a crackdown on a tuition protest at Gezira University south of Khartoum, has sparked the largest outpouring of Arab Spring-style discontent since anti-regime protests in June and July.
Farouk Abu Issa, who represents about 20 opposition parties, told AFP by phone that he had just been taken into custody by the powerful security service.
"I was participating in a forum supporting the students of Gezira University," Issa said.
After giving a speech he returned home and shortly afterwards was detained, he said.
Protests, sometimes involving hundreds of people, have occurred since Saturday outside Khartoum universities and elsewhere in support of the dead youth who were originally from the conflict-plagued Darfur region.
Demonstrators have called for "revolution" and the fall of President Omar al-Bashir's 23-year regime.
The Darfur Students Association has said the four went missing -- and were later found dead -- after taking part in a peaceful sit-in which was disrupted by the pro-government student union.
They were protesting for their "right" to free education, the association said.
Ambassador Dane Smith, the US government's senior adviser for Darfur, said on Wednesday that Sudanese authorities have used excessive force against the Darfuri student demonstrators, whom he said were protesting for their rights.
Smith called the deaths "shocking" and said the protests were "quite reasonable".