Hundreds of angry mourners called for the overthrow of Sudan's government on Wednesday at the funeral of a student allegedly shot dead by security forces at a protest about violence in Darfur.

Ali Abaker Mussa Idris, a third-year economics student, died in hospital from gunshot wounds "after security forces used tear gas and opened fire with live ammunition" at the University of Khartoum demonstration on Tuesday, Amnesty International said.

About 500 mourners, most of them students, gathered Wednesday at a cemetery in South Khartoum waiting for the victim's body to arrive, an AFP reporter said.

"The people want to overthrow the regime," they called, in a reference to the 25-year rule of President Omar al-Bashir, who seized power in an Islamist-backed coup.

The student's death, they said, heralded a "revolution".

"No dialogue without freedom!" they said in an apparent reference to Bashir's appeal for a wide-ranging national dialogue on the future of the country ravaged by armed insurrection, poverty and political turmoil.

"A million martyrs for a new dawn!" the mourners called.

About 300 students, many of them from Darfur, protested at the university on Tuesday.

Police said they fired only tear gas when the rally tried to move out of the campus onto surrounding streets.

The unrest was the most serious in Khartoum since last September, when thousands of people demonstrated after the government slashed fuel subsidies.

Amnesty International said security forces were believed to have killed more than 200 people at that time, many of them shot in the head or chest.

Authorities reported a toll of less than half that.

An 11-year-old rebellion continues in Sudan's western Darfur region but inter-communal fighting, typically between Arab militias, has now become the major source of violence.