TEHRAN — Police fired tear gas on Monday at Iranian protesters gathered in central Tehran chanting slogans against President Mahmoud Ahmadinejad, witnesses said, as the nation marked Students Day.

The clashes came as a group of Iranian students issued a call for mass protests against Ahmadinejad to coincide with the annual event.

"Police fired tear gas at groups of protesters chanting slogans against President Mahmoud Ahmadinejad in Vali Asr intersection and Enghelab Street," a witness told AFP, referring to prominent locations in central Tehran.

The protesters were chanting "Death to the Dictator" and "Do not be scared. We are all together," the witness said, adding that some protesters also beat up a policeman.

AFP could not independently confirm the incidents as foreign media have been banned from covering Monday's event.

Students of Tehran's prestigious Amir Kabir University had earlier urged protests against Ahmadinejad, in an online statement.

"We are asking all people to come to universities so we can have one voice to protest at the coup d'etat," said the statement, issued by the group going under the name "Green university students of Iranian universities."

To read full AFP story � Go Here Now.