TEHRAN- Unidentified men opened fire this week on leading Iranian opposition figure Mehdi Karoubi, an opposition website reported on Friday.

Karoubi, a defeated candidate in presidential elections last June, was attacked in the city of Ghazvin, 124 km (70 miles) west of Tehran, on Thursday after visiting a cleric, Nasir Ghavami, the website Kaleme said.

Kaleme is run by supporters of Mirhossein Mousavi, an opposition leader who also lost out to President Mahmoud Ahmadinejad in the June vote. There was no confirmation in state-run media about the incident and no officials were available to comment on the Iranian weekend.

While leaving Nasi Ghavami's home the plainclothes men attacked his car with eggs and bricks as well as firing two shots which hit the car, Karoubi's son Hossein was quoted as saying.

One of the two shots hit the windshield and the other hit the back window. Since the car was bulletproof, the glass cover of the back window was broken and the (front) windshield was cracked.

Iran has seen its most serious domestic unrest since the Islamic revolution in 1979, as opposition supporters stage protests against the election result that have turned violent. Authorities deny opposition charges that voting was rigged.

Mousavi's nephew was shot dead by an unidentified assailant during street clashes on December 27.

Hardline clerics and authorities have called on the judiciary to punish opposition leaders for igniting tension in Iran, saying they were 'mohareb', an Islamic term meaning warring against God which carries the death penalty.

The stakes are high because Ahmadinejad has championed a nuclear energy policy that has led the country, a major oil producer, into conflict with the West, bringing United Nations sanctions to bear on a stretched economy.

Iran rejects U.S. charges that it plans to develop nuclear weapons, saying its program is aimed at producing electricity.