More than 5,000 people gathered across the weekend in Milan, where police deployed tear gas and water cannons after protesters, many wearing masks, threw paving stones, bins and chairs at officers. Clashes began on Saturday and continued into Sunday.
"To demonstrate is a right. To lay our cities to waste is not," Meloni said on Saturday, adding that "hooligans" had exploited the protests to "sow chaos". The rioting broke out on the sidelines of mostly peaceful youth-led protests that have also occurred in France, Spain and Albania.
Milanese Mayor Giuseppe Sala said he was worried the violence was a "new phenomenon" that "originates from an international scenario and therefore feeds itself". Speaking to Italian news agency Ansa, he described witnessing "smashed shop windows, looted stores, and frightened citizens", and said "what happened here is what we are seeing in many cities around the world".
More than 200 people were detained, 80% of whom were minors, Ansa reported. The city's prosecutor's office has requested prison sentences for five adults arrested for looting, vandalism and resisting arrest, according to Italian news agency AGI. Italian media reported that people, including police officers, were injured.
Violence between protesters and police also rippled into other northern cities. Meloni said people in Turin were detained while "carrying cobblestones and window-breaking hammers", while a train station in Bologna was closed as a precaution after similar disorder.
The prime minister, who faces an election next year, also called on her political opponents to condemn the rioting. "Do not be ambiguous about this," she said on X, explaining that condemnation must be "unanimous" because "any hesitation becomes justification".
Democratic Party leader Elly Schlein said her party had always condemned violence and that the rioting should not be used to stifle the voices of peaceful protesters across the country who are struggling to make a living, Ansa reported.
The violent disorder followed anti-government protests held by students in various Italian cities on Friday, and echoed similar unrest in neighbouring France, where hundreds of thousands took to the streets.