LONDON - Iran has detained scores of students in an apparent bid to prevent new opposition protests during annual Student Day events next month, a Western-based human rights group said.

Iranian police, seeking to avoid any repeat of the huge demonstrations that erupted after a disputed election in June, have warned opposition supporters against using the December 7 Student Day commemorations to hold more rallies.

The pro-reform opposition says the June 12 presidential poll was rigged to secure hard-line President Mahmoud Ahmadinejad's re-election. The authorities reject vote fraud allegations.

The International Campaign for Human Rights in Iran, based in the West, said scores of students in Iran had been detained and prosecuted in recent days, as authorities apparently seek to stifle protests expected on December 7.

The group's spokesman, Hadi Ghaemi, said in a statement published late on Tuesday: In order to silence the student movement, a wholesale crackdown on Iranian students is underway, which not only violates their rights, but also disrupts their studies and the lives of their families.

Reformist web sites in Iran have also reported on detentions of students in recent weeks, saying some have also been suspended from their studies.

Getting closer to Student Day, pressure on students has increased to prevent them from holding gatherings on that day. Around 60 leading students have so far been arrested, the pro-reform Norooz web site said.

Iran regularly dismisses accusations of human rights violations and accuses its Western foes of double standards and of violating people's rights in their own countries.

Unable to stage their own demonstrations, reformers have sought to hijack official protests and have urged supporters to turn out on December 7.

Police clashed with supporters of Mirhossein Mousavi, who came second to Ahmadinejad in the June vote, on November 4 when an official rally marking the 30th anniversary of the storming of the U.S. embassy turned violent.

On Sunday police prevented a mourning ceremony for the killing in 1998 of the heads of the illegal but tolerated Iran Nation Party from turning into an opposition rally.

Thousands have been arrested since the election for fomenting protests, which the authorities have portrayed as part of a foreign-backed bid to undermine the Islamic Republic's clerical establishment.

Most of have been freed, but Iran's judiciary last week said 81 people have so far been sentenced to jail terms of up to 15 years in connection with post-election unrest. Five people have been sentenced to death.

(Editing by Jon Hemming)