WASHINGTON -- The White House on Wednesday expressed concern about a violent crackdown on anti-government protesters in Iran as President Obama said he wanted the United States 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 counterdemonstrations 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 told The Associated Press that security forces swept through a gathering of hundreds of demonstrators by clubbing, kicking and slapping protesters. 

The unrest came 30 years after militant Islamic students stormed the embassy in Tehran. With support from the Iranian government, 52 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. 

"This event helped set the United States and Iran on a path of sustained suspicion, mistrust and confrontation," Obama added. "I have made it clear that the United States of America wants to move beyond this past, and seeks a relationship with the Islamic Republic of Iran based upon mutual interests and mutual respect. ... We have made clear that if Iran lives up to the obligations that every nation has, it will have a path to a more prosperous and productive relationship with the international community." 

The Iranian government backed events Wednesday 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. 

Simultaneous anti-government marches were stormed by Iranian security forces using batons and tear gas, witnesses and state media reported. 

Obama praised opposition protesters who have taken to the streets to speak up for change. "The American people have great respect for the people of Iran and their rich history," Obama said. 

"The world continues to bear witness to their powerful calls for justice and their courageous pursuit of universal rights."