Reuters - Police used gas to disperse protesters at the Group of 20 summit in Pittsburgh on Thursday as about 2,000 people marched despite warnings that force would be used to break up the demonstration.

Leaders of 19 leading developed and developing economies and the European Union meet on Thursday and Friday for a G20 gathering to discuss how to improve financial reforms to avoid another global economic crisis.

“You must leave the immediate vicinity regardless of your purpose,” police told protesters over bullhorns about an hour into the march.

Police then cautioned that tear gas and other “non-lethal force” would be deployed.

With protesters sent down various streets by police, the two sides eventually clashed in Lawrenceville, about a mile (1.6 km) from where the G20 talks were taking place.

Protesters threw bottles and police responded by sending five to 10 canisters into the crowd. The sharp smell of the gas irritated the eyes and throats of protesters, causing them to flee.