NAIROBI -- Kenyan police firing rifles in the air fought running battles on Friday with rock-throwing protesters angry at police over the killing of a fellow student, witnesses said.

"Go Home, Go Home," demonstrators chanted as they swarmed over public roads near university dormitories in the worst student confrontation with police for at least a year.

Police fired dozens of shots in the air, as well as tear gas canisters and rubber bullets, to suppress the demonstration by 300 to 400 university of Nairobi students, the witnesses said.

Police killed the fourth-year student on Thursday, saying he had drawn a knife and charged them rather than surrender during the raid of a drugs den near the university.

Police said they fired twice in the air before shooting the unidentified student.

Students, who stoned and set cars alight late on Thursday in downtown Nairobi to protest against the killing, said the police killed an innocent man a week before his final examination.

"We are angry, we want revenge," said a science student.

"The police surely planted evidence that there was bhang (cannabis). Our colleague was shot but there was no issue of bhang," said one angry student who declined to be identified, holding a rock to throw at police.

The students regularly stone passers-by, loot and smash cars and light street bonfires in protest against ordinary failings in dormitory amenities such as power cuts or food shortages.