Police in Geneva have fired tear gas and used water cannon after parts of a largely peaceful demonstration against the G7 summit in nearby Evian, France, descended into clashes.

About 20,000 people took to the streets of the Swiss city on Sunday to denounce the gathering of leaders from the world’s richest democracies, which opens on Monday across Lake Geneva in the French spa town.

Authorities had authorised a march on a route far from the luxury shops of central Geneva, hoping to avoid a repeat of the riots that scarred the city during the 2003 G8 summit.

Most demonstrators marched calmly under a blazing sun, waving Palestinian flags and climate banners and chanting against capitalism and Western military alliances. Placards read, “No to the G7 and all imperialist alliances” and “Abort the G7.”

“I’m here because I don’t accept that this small group of leaders makes decisions that affect all of us,” said Michel, a 69-year-old Swiss retiree carrying a Palestinian flag.

Tensions spiked when groups of black-clad protesters broke away from the main march, smashing barriers, attacking upmarket apartment blocks and setting cars on fire. A Tesla vehicle was seen burning with the slogan “Eat the Rich” sprayed on its side while buildings near the European headquarters of the United Nations were damaged.

Police said about 600 “Black Bloc” activists were involved in the violence.

The summit – one of the first major international meetings since the United States and Israel launched a war against Iran in February – is expected to be dominated by efforts to halt that conflict and by Russia’s war in Ukraine.

French President Emmanuel Macron arrived in Evian on Sunday to host US President Donald Trump and other G7 leaders as thousands of Swiss and French security personnel were deployed around the lake region.