Dozens of people including pro-government militia have tried to attack Italy's embassy in Iran, Italian Foreign Minister Franco Frattini says.
Basij militia dressed as civilians hurled stones and shouted "Death to Italy" and "Death to Berlusconi", he told a senate hearing.
Iranian media said a protest took place but made no mention of violence.
Tensions have been high in Tehran since President Mahmoud Ahmadinejad's disputed poll win last year.
Correspondents say the protest could be linked to Italian Prime Minister Silvio Berlusconi's pledge of support for Israel and his call for sanctions against Iran to be tightened, during a visit to Jerusalem last week.
Italian energy company ENI has already said it will pull out of Iran.
Italy is Iran's biggest trading partner in the European Union.
Western powers have stepped up pressure on Iran over its nuclear programme, but Tehran says it has started the process of enriching uranium to 20%.
Speaking at a senate committee hearing on Iran, Mr Frattini said about 100 "hostile" protesters threw eggs and stones at the Tehran embassy but were prevented by police from getting inside.
There was "no significant damage", he said.
Iran's privately-owned Fars news agency said the protesters "condemned the actions of the [Italian] government in supporting seditionists and interfering in Iran's internal affairs".
Protests also took place outside the French and Dutch embassies.
Mr Frattini said Italy had cancelled its attendance on Thursday at events marking the anniversary of the Iranian revolution.
"Contacts are under way at the European level" aimed at sending a "signal of strong concern" over the incidents, he added.