RIOT (EPA) –Iranian anti-riot police fired tear gas among protestors holding signs criticizing the administration of Iranian President Mahmoud Ahmadinejad on the streets of Tehran.

TEHRAN (AFP) – Riot police waded in with batons and teargas to break up opposition protests in Tehran on Wednesday, as huge crowds staged a noisy anti-US rally nearby to mark the storming of the American embassy by students 30 years ago.

Witnesses said the clashes occurred at Haft-e-Tir Square in the heart of the capital, where several hundred opposition supporters had gathered mid-morning to stage a demonstration.

Riot police roared in on motorcycles and fired teargas at the protesters, who were chanting "Death to the dictator."

When they refused to disperse, police moved in with batons, beating and arresting dozens of people as groups of pro-government hardliners stood by chanting "Death to America."

The opposition website reported that opposition leader Mehdi Karroubi was among the protesters at the square but left quickly after he and his supporters came under attack by the hardliners.

The White House said the United States hoped "violence will not spread" and that it was following the events "clearly and closely."

French Foreign Minister Bernard Kouchner said he was "worried" and the developments were "not a good omen, a government that represses at home and refuses dialogue outside."

AFP reporter Farhad Pouladi was detained by security force members in the center of Tehran, witnesses said. He was detained after being stopped by three security personnel, two in uniform and one in plainclothes.