Tehran, Iran ? President Mahmoud Ahmadinejad claimed to be delighted when reformist students disrupted his visit to their elite university in December, burning his portrait and shouting “Death to the dictator!”

It showed the world that Iranians can protest “with an absolute, total freedom,” the hard-line president wrote on his Web site.

But at least eight of Amir Kabir University’s leading reformists have been arrested since May, according to their lawyers and activists inside and outside Iran.

They are among hundreds rounded up in recent months in a nationwide crackdown on those accused of threatening the Iranian system.

Two years after Ahmadinejad’s election, the “Tehran Spring” of his moderate predecessor, Mohammad Khatami, is a fading memory. A deep chill has settled over those pushing for change inside the Islamic Republic.

Some dissenters blame the crackdown on the regime’s fear of a U.S. effort to undermine it as tensions over Iran’s nuclear program intensify. Others say the intent is simply to contain discontent fueled by a faltering economy.

Teachers, feminists, union leaders, journalists, students and at least four Iranian-Americans have been arrested over roughly the last six months.

Most have been freed after spending days, week or months behind bars. But many of their cases remain open in Iran’s revolutionary courts, a parallel justice system that operates with few of the protections available in civilian courts, lawyers and activists said.

“The new government has increased pressures on the nation – students, laborers, intellectuals,” said Ebrahim Yazdi, foreign minister after Ayatollah Ruhollah Khomeini’s 1979 revolution and now leader of the banned but tolerated Freedom Movement of Iran.

“When laborers stage protest rallies, the government, instead of talking to them, takes them to jail. Women are jailed just for collecting signatures in support of women’s rights,” he said in an interview with The Associated Press.

Restrictions in Iran are far from absolute.

Iranians criticize the government in public, and ignore a wide array of social regulations at home.

Defenders of the system point out that is more open than in many nations in the region, including some of America’s allies.