The main university in the Zimbabwean capital, Harare, has been closed indefinitely following several days of demonstrations by students calling for President Mugabe's resignation.

Thousands of students have been sent home and riot police are patrolling the city centre.

One report said police entered the University of Zimbabwe campus after overnight disturbances, and fired teargas to disperse the protesters.

The students, who began demonstrating last week, are demanding an increase in grants and an end to what they say is widespread government corruption.