This is not the first time that the militant Ansar-e-Hizbollah takes the law into its own hands and attacks meetings which it deems to be against the interests of the Islamic Republic. Since President Khatami came to power in last August, the group repeatedly resorted to violence and attacked cinemas, university gatherings and dissident figures.

Some supporters of President Khatami have condemned the group and criticised the Iranian police and intelligence forces for not taking action against them. Because the group has several open publications and its leaders are known, it's suspected that they have powerful friends in the establishment who are protecting them.

It's also been suggested that some conservative organisations are using them to undermine President Khatami, who has been trying to introduce more freedoms. The fact that the police force in Iran is controlled by the supreme leader, Ayatollah Khamenei, adds to Mr Khatami's problems.