Thousands of demonstrators repeatedly clashed with police - who responded with batons, pepper spray and water cannons - as they marched through the streets of the capital on Saturday.

The demonstrators tried to break through barricades, throwing chairs and firecrackers.

Four people were initially arrested amid the chaos, news agency ANSA reported.

In the early evening, protesters stormed the headquarters of Italy's largest trade union, CGIL.

Amateur footage showed them attacking guards and police with sticks and flagpoles, then pushing through the door into the building.

Italian Prime Minister Mario Draghi condemned the violence and underlined that trade unions are guarantors of democracy and workers' rights, and that any attempt of intimidation must be severely punished.

CGIL general secretary Maurizio Landini called the attack an "organised act of fascist violence, an attack against democracy and against the whole business world, which we will repel. No one must think they can push our country back to the fascist era".

New measures against COVID-19 will come into force next week in Italy.

From October 15, every employee in the private or public sector must have a so-called 'green pass', which shows proof of vaccination, recovery from or a negative test for the virus

Green pass critics and vaccination opponents have been campaigning against the measure, introduced to allow further COVID-19 relaxations from Monday.

Cinemas, theatres and concert halls will be allowed to operate at 100 per cent capacity again, while nightclubs can also reopen. Admission is only possible with the green pass.

Australian Associated Press