About 200 Cambodia National Rescue Party supporters showed up for the planned local government campaign rally near Phnom Penh's Freedom Park, which was sealed off with barbed wire and guarded by police and civilian security auxiliaries, who are armed with clubs and other homemade weapons and are often employed by the government to break up protests.
Fighting appeared to break out when demonstrators taunted the security forces, who responded by chasing and beating people. At least five people were hurt, including an opposition supporter, a Buddhist monk and a local journalist.
Security forces beat about half a dozen people Thursday in the same area after a May Day rally held jointly by the opposition and labor activists.
Public demonstrations have been generally banned in Phnom Penh since January, after labor protests for a higher minimum wage and opposition demonstrations denouncing last July's general election as rigged posed a political challenge to the government.
Opposition party lawmakers have boycotted their seats in the National Assembly, but both the opposition and the government of Prime Minister Hun Sen have said they are close to a deal which would include electoral reforms and moving up the date of the next election.
Hun Sen has been in power for almost three decades, and while Cambodia is formally democratic, his government is authoritarian and known for intimidating opponents.