By NASSER KARIMI

TEHRAN, Iran (AP) – Iranian security forces intensified their crackdown on anti-government supporters Tuesday, arresting relatives of the country’s Nobel laureate and the main opposition leader, and limiting the movement of another top opposition leader.

Iran also accused the U.S. and Britain of fomenting the recent violence. Clashes on Sunday left at least eight people dead in a confrontation that has become an increasingly bitter and violent.

Government supporters held rallies in at least three cities on Tuesday, many protesting against the opposition and its leaders.

Opposition Web sites reported about 10 new arrests, and those taken into custody included the sister of Shirin Ebadi, who won the 2003 Nobel Peace Prize for her human rights efforts in Iran.

The new arrests, along with the tough criticism of the U.S. and Britain, added to rising tensions with the West, which is threatening to impose tough new sanctions over Iran’s suspect nuclear program and has criticized the violent crackdown on anti-government protesters.

The opposition Greenroad Web site also reported additional arrests, among them opposition leader Mir Hossein Mousavi’s brother-in-law, Shapour Kazemi, and Mashallah Shamsolvaezin, a journalist who frequently criticizes the government. Others included the son of a prominent ayatollah, a reporter for the semiofficial ILNA news agency, and several activists. Mousavi’s nephew was among those killed this week.

There was no serious violence reported Tuesday, but the Greenroad Web site said students and security forces clashed at the Azad University’s science department in Tehran.

It cited witnesses as saying the students were later “locked down” inside the building while pro-government Basij militiamen threatened to arrest those who dared to leave the premises.

Sunday’s clashes were the worst since the aftermath of June’s disputed presidential election. In outbursts of fury rarely seen in past street confrontations, protesters burned squad cars and motorcycles belonging to security forces who had opened fire on the crowds, according to witness accounts, opposition Web sites and amateur videos posted on the Web.

The exact death toll from Sunday’s violence remains unclear. The government had said eight people were killed, but on Tuesday, Tehran’s chief prosecutor said he was investigating only seven deaths.

Britain, France, Germany and the U.S. have criticized Iran’s violent response to the protests. On Monday, President Barack Obama praised “the courage and the conviction of the Iranian people” while condemning Iran’s Islamic government for attacking demonstrators with “the iron fist of brutality.”