Brisbane will operate a 24-hour, week-long G20 court to deal with expected mass arrests during the leaders' summit in mid November, Xinhua news agency reported.

The 24/7 court follows threats by protest groups who say property destruction is a legitimate form of protest and that their followers should "smash the G20".

The court will begin on Nov 10, five days before the start of the two-day summit of world leaders with police expecting violence from protesters.

The court plan follows a model used by Toronto police in Canada in 2010 when more than 1,100 people were arrested.

G20 operational police commander, Assistant Commissioner Katarina Carroll said authorities wanted offenders in Brisbane "processed and in front of a
magistrate as soon as possible."

"We have convened 24/7 courts so that those arrested are not detained for longer than is necessary," she said.

With only three weeks to go, activists have vented online that peaceful protests are ineffective and threatened destruction of property.

"We are encouraging individuals and groups to take action which they see as effective and necessary given their circumstances. We do not see property destruction as an inherently violent act," some activists said on their website.

Anarchist community group Autonomous Action Radio has created an online poster that depicts hooded and masked protesters who appear to be holding molotov cocktails, hurling objects and overturning a bin.

"Smash the G20. For decentralised attacks on capital in mid November," reads the poster which copies a similar image used in the Pittsburgh G20 summit of five years ago.