Several thousand people have taken to the streets of the Iranian capital, Tehran, to mark the anniversary of violent street protests three years ago.

The protesters defied a government ban on any gathering to commemorate the riots, which were sparked by a police raid on a student dormitory.

There were sporadic clashes and some demonstrators were arrested or beaten, but no serious injuries were reported.

The BBC Tehran correspondent, Jim Muir, says the disturbances reflect widespread dissatisfaction with the regime but do not amount to a serious threat to it.

Student fears

The skirmishes are reported to have gone on for several hours before dying down.

A raid on a student dormitory sparked the 1999 riots

In several major squares, the demonstrators clashed with security forces, police and right-wing vigilantes.

And, in some places, police fired teargas to disperse the protesters.

The main student organisation, which backs the reform movement, had earlier cancelled plans to mark the anniversary for fear that the occasion might be exploited by provocateurs.

Many of those taking part in the commemoration were not young students, but middle-aged and even elderly people, some of them wearing ties to symbolise their attachment to the era before the Islamic Revolution.

Police raid

Many students and other backers of the reform movement are deeply frustrated at the lack of progress since they helped elect President Mohammed Khatami five years ago.

He has been working with a parliament that is also reformist dominated. But hardline conservatives still control mechanisms which can and do block reformist legislation.

The conservatives' control of the judiciary and much of the security apparatus has often made the reformists appear to be in opposition rather than in power.

The unrest in 1999 was sparked by a raid on a student dormitory by police and right-wing vigilantes in which one student was killed and dozens injured.

It led to some of the worst disturbances in Iran since the Islamic revolution.