MOSCOW (AP) — The Russian opposition Parnas Party says its leader, Mikhail Kasyanov, has been attacked while on the campaign trail in southern Russia.

Kasyanov's party is one of the few opposition forces allowed to run in Russia's Sept. 18 parliamentary election.

A party spokeswoman told The Associated Press that several dozen men attacked Kasyanov and his supporters when they arrived for a campaign event Wednesday in the southern city of Stavropol. The party press office said the same group follows Kasyanov on his campaign trail and confronts him and his supporters outside events, either shouting abuse or physically attacking people.

The party said no injuries were reported Wednesday.

Attacks on opposition leaders in Russia have become widespread in recent years as state-owned media often brand them as "fifth columnists" and "traitors."