PITTSBURGH — An unpermitted march at the Group of 20 summit in Pittsburgh turned chaotic this afternoon, with protesters rolling trash bins toward police and officers firing gas in return.

Some protesters also are using pallets and corrugated steel to block a road.

Protesters exposed to the gas were coughing, complaining of eyes watering and stinging.

The march does not have a city permit and police have declared it an unlawful assembly.

Several hundred protesters, many advocating against capitalism, had been trying to march toward the site of the summit.

The group broke into smaller groups after being confronted by police.