Hundreds of Zimbabwean students fought running battles with the police this week after the death of one of their colleagues at the hands of soldiers.
Their attempts to march into the capital Harare to join a civil-rights protest were physically thwarted by the authorities.
Students were incensed by the death of Lameck Chemvura, a 22-year-old student who was allegedly strangled with a shoelace and thrown from a moving train by soldiers. He was accused of supporting the opposition Movement for Democratic Change.
Police told the state-controlled newspaper, The Herald , that Mr Chemvura's death occurred during a brawl and was not politically motivated. Spokesman Wayne Bvudzijena said a soldier had been arrested and charged. But witnesses reported seeing six soldiers throw the young man from a train, and students do not believe the official explanation.
On Tuesday, 11 students from the University of Zimbabwe and 28 civil-rights activists were arrested for trying to demonstrate against proposed amendments to electoral laws, a police spokesman said.
A university lecturer, who did not want to be named, claimed riot police fired tear gas at protesting students, who "retaliated with stones". Police sealed off approaches to parliament and to the University of Zimbabwe to prevent the protest.
Student leader Tapera Kapuya was among those arrested. The students were charged with malicious injury to property, police said, and end-of-year examinations were postponed.
This week's events are the latest in a saga that has unfolded over the past year. Students have been rallying against government clampdowns on the judiciary and the press, against attacks on students and opposition parties ahead of presidential elections early next year, and against inadequate state allowances.