Protesters threw smoke bombs and clashed with police in central Rome on Wednesday while Italian Prime Minister Enrico Letta met French President Francois Hollande in the capital.
The scuffles broke out around the Campo de' Fiori central square where people had gathered to protest against a high-speed rail link being built between France and northern Italy.
Baton-wielding police pushed a group of shouting protesters down a narrow street that leads away from the square. Demonstrators threw bottles and flares at the police.
The Italian government says the rail line, which will almost halve the time of a journey between Paris and Milan to four hours, is vital to strengthen transport links between Italy and the rest of the continent.
But opponents to the plan worry about its environmental impact and question whether Italy should be spending billions on such a large-scale project when they could be using it to help families struggling in a recession which has lasted more than two years.
Protesters also targeted offices of Letta's Democratic Party (PD), hurling firecrackers and chanting "Out Out" after Italian Justice Minister Anna Maria Cancellieri earlier survived a no-confidence vote in parliament.
Cancellieri has faced calls to resign in recent weeks over accusations that she used her influence to get the daughter of a disgraced insurance magnate out of prison. She defended herself in parliament against the claims on Wednesday.
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