An illegal march at the G20 summit in Pittsburgh turned chaotic today, with protesters rolling dustbins toward US police and officers firing tear gas in return.
Some demonstrators also used pallets and corrugated steel to block a road.
Protesters exposed to the gas were coughing and complaining of their eyes stinging and watering.
The march did not have a city permit and police declared it an unlawful assembly.
Several hundred protesters, many loudly denouncing capitalism, had been trying to march toward the site of the summit.
The marchers split up into smaller groups after being confronted by police.