TEHRAN, Iran -- About 1,000 supporters of Iran's hard-line clerics took to the streets Friday calling for the execution of a reformist scholar convicted of insulting Islam.

The sentence against Hashem Aghajari, a history professor who challenged the ruling clerics' interpretation of Islam, has touched off the biggest protests in Tehran in three years, with thousands of university students demanding the reversal of his death sentence.

His case has heightened tensions in the power struggle between reformists who seek more social and political freedoms and Islamic hard-liners, who control the police and judiciary and the strongest levers of power in Iran.

Hossein Allahkaram, leader of the hard-line group Ansar-e-Hizbollah that led Friday's demonstration, said Aghajari had renounced his religious faith and deserved death.

"He insulted the principles of our religion and must be hanged," he said.

Aghajari called for restraint from his supporters during a meeting with his family members in a prison in the western city of Hamedan, his daughter, Sara Aghajari, told The Associated Press Friday.

"Some people want to promote tension and inflame student movements. They are expected to seek their demands within the framework of the law," she quoted her father as saying.

In a June speech, Aghajari said that each generation should be able to interpret Islam on its own and that the word of clerics in the past need not be taken as sacred.

Aghajari has decided not to appeal the death sentence issued last week, challenging hard-liners to carry out his execution, his attorney, Saleh Nikbakht, said Wednesday.

Iran's pro-reform president, Mohammad Khatami, said Wednesday the verdict "never should have been issued at all" and urged the case be "settled in a favorable manner to avoid any problems in the country."

The hard-line judiciary issued a statement saying it would defend Aghajari's conviction.

The sentence will be considered final on Dec. 2 unless Aghajari appeals or the judge or prosecutor general reverses it.