In Bologna, clashes broke out between some demonstrators and police on Saturday evening, the Italian newspaper Corriere della Sera reported.
Emergency medical services received 17 calls for assistance, and six people were taken to hospital by ambulance, Xinhua reported.
In Rome, demonstrators set off from Piazza della Repubblica on Saturday afternoon for an anti-war march, according to the ANSA news agency. Clashes erupted between protesters and police in the city center later in the evening, prompting police to use water cannons and tear gas in an attempt to disperse the crowds.
In Turin, demonstrators protesting mainly against increased military spending and rising fuel prices clashed with police on Saturday evening. Some protesters threw fireworks and bottles at officers, who responded by firing tear gas.
Following demonstrations that escalated into riots and looting last weekend, particularly in Milan, Italian Interior Minister Matteo Piantedosi ordered additional police forces to be deployed across the country. The reinforcement was focused particularly on major cities where the largest rallies were expected.
Italian Prime Minister Giorgia Meloni condemned the violence in a social media post on Saturday evening, stressing the need to protect both peaceful demonstrators and the wider public.
"Everyone's safety must be guaranteed: those who wish to demonstrate peacefully, those who work, and those who want to live in their cities without fear," she said. "We must leave no room for those who seek nothing but confrontation and violence."