About 5,000 demonstrators marched from the city's town hall to Hyde Park several blocks away, amid a strong police presence and city lockdown.
The protest took place ahead of the start of the annual APEC in Sydney on Saturday and Sunday, at which leaders of the forum's 21-member economies are expected to discuss global warming, global trade liberalization and food hygiene.
Police water cannons and riot vehicles have been on hand amid expectations of violence, but the rally has proved to be largely peaceful so far.
Five people have been arrested by the police, however, and two policemen injured, a police spokeswoman told Kyodo News.
One of the policemen had to be taken to a hospital to be treated for a head injury, she said.
Further details of the incident are not yet known, but the spokeswoman confirmed reports that two of the protesters were "scantily clad" streakers.
Event organizers from the Stop Bush Coalition urged protesters not to be provoked by the police or other demonstrators during the event.
The rally had been well publicized ahead of the APEC summit, but there had been some doubt earlier this week whether it would be allowed to go ahead, after police launched a successful court action to have the route altered away from a planned sweep past the U.S. consulate.
AP - Kyodo
Last Mod: 08 Eylül 2007, 10:44