An Iranian university professor sentenced to death for insulting Islam appealed the verdict on the last day before it became final, state-run Tehran radio reported Monday.

Hashem Aghajari had previously refused to appeal his sentence, challenging the judiciary to carry it out. The sentence had prompted weeks of protests by students who criticized the judiciary.

"Hashem Aghajari's lawyer lodged an appeal Monday morning on the last day of a 20-day period," the radio quoted judiciary official Zekrollah Ahmadi as saying. It gave no further details.

Aghajari, a history professor at Tarbiat-e-Modarres, or Teachers Training University in Tehran, was sentenced to death last month by a court in the western city of Hamedan after being convicted of insulting Islam and questioning the hard-line clergy's rule.

Aghajari's case highlights the power struggle between reformists supporting President Mohammad Khatami's program of social and political freedoms and hard-liners who control unelected institutions, including the police and judiciary.