WASHINGTON — The White House today expressed concern about a violent crackdown on anti-government protesters in Iran as President Barack Obama said he wanted U.S. and Iran to move beyond "suspicion, mistrust and confrontation."

Iranian security forces clubbed anti-government protesters with batons on the sidelines of state-sanctioned rallies to mark the 30th anniversary of the U.S. Embassy takeover. The counter-demonstrations were the opposition's first major show of force on Tehran's streets in nearly two months.

"We obviously have seen and are following the reports of this, and hope greatly that violence will not spread," White House spokesman Robert Gibbs said.

Witnesses said security forces swept through a gathering of hundreds of demonstrators by clubbing, kicking and slapping protesters.

The unrest came 30 years after Islamic militants stormed the embassy in Tehran. Fifty-two Americans were held hostage for 444 days.

The crisis "deeply affected the lives of courageous Americans who were unjustly held hostage, and we owe these Americans and their families our gratitude for their extraordinary service and sacrifice," Obama said in a statement issued late Tuesday.

The Iranian government backed events today to commemorate the anniversary of the takeover, including an annual anti-American rally outside the brick walls of the former embassy compound.

Thousands of people gathered outside the former embassy, waving anti-American banners and signs praising the Islamic Revolution.