Italian police battle rioters in Milan at start of Expo

The takeoff for the World Expo 2015 in Milan was overshadowed by violent protests.  Thousands of protesters marched through the streets of Milan, behind a banner reading ‘No Expo, Eat the Rich’.

Police fired tear gas at the demonstrators as thick clouds of smoke from burning cars filled parts of central Milan, where groups of protesters, their faces masked against the fumes, threw stones and petrol bombs and faced off against lines of police in riot gear.

The confrontation broke out after an opening ceremony at the Expo site where Prime Minister Matteo Renzi hailed the start of a six-month-long showpiece of culture and technology that focused on the theme of sustainable food production.

The fair mobilised a range of left-wing protesters, from anti-globalisation and environmentalist activists to students and anti-austerity campaigners, who see it as a symbol of waste and corruption. Thousands of police had been deployed to counter the threat of violence.

Renzi has been counting on the event to reinforce signs of recovery after years of recession that have hit young people especially hard.

"All you experts who kept saying 'We'll never do it' -- this is your answer," he said at the opening. "I like to think that tomorrow begins today."

The event had already been hit by a corruption investigation that saw several officials arrested and by cost overruns and construction hold-ups. Large parts of the site were not ready for opening day.

Pope Francis, who spoke via a televised link-up to the opening ceremony, referred to the irony of a global spectacle dependent on corporate sponsorship deals being devoted to sustainable development and feeding the poor.

"In certain ways, the Expo itself is part of this paradox of abundance, it obeys the culture of waste and does not contribute to a model of equitable and sustainable development," he said.