A group of around 100 protesters threw firecrackers, smoke bombs and bottles at police after breaking away from the main body of a demonstration in the Olympic host city of Milan on Saturday.

Police in riot gear and with shields responded with water cannon to try to disperse the group, some of whom wore hoods and scarves to cover their faces. Order was restored after a few minutes.

Six people were detained during the skirmishes, police sources said.

An estimated 10,000 people took to the streets of Milan in a protest over housing costs and environmental concerns on the first full day of the Milano Cortina Winter Olympics.

The march, organised by grassroots unions, housing-rights groups and social centre community activists, is seeking to highlight what activists call an increasingly unsustainable city model marked by soaring rents and deepening inequality.

Security in Italy’s financial capital had been tightened for the Games.

The demonstration was seen as a flashpoint after a rally last weekend by the hard-left in the city of Turin turned violent, with more than 100 police officers injured and nearly 30 protesters arrested, according to an interior ministry tally.

Left behind by Milan’s boom

The Olympics cap a decade in which Milan has seen a property boom following the 2015 World Expo, with locals squeezed by soaring living costs as an Italian tax scheme for wealthy new residents, alongside Brexit, draws professionals to the financial capital.

Some groups also argue that the Olympics are a waste of public money and resources, pointing to infrastructure projects they say have damaged the environment in mountain communities.

“I’m here because these Olympics are unsustainable - economically, socially, and environmentally,” said 71-year-old Stefano Nutini, standing beneath a Communist Refoundation Party flag.

He argued that Olympic infrastructure had placed a heavy burden on mountain towns hosting events in the first widely dispersed edition of the Winter Games.

The International Olympic Committee says the Games are largely using existing facilities, making them more sustainable.

At the head of the procession, about 50 people carried stylised cardboard trees to represent the larches they said were felled to build a new bobsleigh track in Cortina d’Ampezzo.

“Century-old trees, survivors of two wars ... sacrificed for 90 seconds of competition on a bobsleigh track costing 124 million (euros),” read another banner.