Hundreds gathered in Rome on Tuesday to protest against the arrival of Roma (Gypsy) families at a government-run centre, triggering violent protest.
A group of 70 Roma, including dozens of women and children, were set to be transferred temporarily to a reception centre in the east of the city.
But shortly after this was announced demonstrators blocked the centre’s entrance and set fire to a car.
Prosecutors are now investigating the incident.
The city’s mayor, Virginia Raggi, ordered the investigation and said there was a “very heavy climate of hatred” at the protest, which was reportedly organised by two far-right groups.
She said the families had now been housed elsewhere.
Video shared on local media showed people setting up barricades to prevent the families from reaching the reception centre.
Footage published by the newspaper La Repubblica also showed people destroying food that was reportedly meant for the families. One person can be heard shouting: “They must die of hunger!” in the clip.
“I intervened to stop the situation degenerating,” Ms Raggi said of the incident. “I intervened to protect the very many honest citizens of that [area] and the 33 children [among the Roma],” she added.
Deputy Prime Minister Matteo Salvini condemned the violence but repeated his pledge to clear all Roma camps in Italy.
“The goal that I have been working on for months is to have no Roma camps by the end of my term as minister,” he told the Ansa news agency.
Mr Salvini and allies in his right-wing League party have accused Roma of stealing and preferring to stay on the margins of society.
Italy’s Roma community mostly live in poverty; there are at least 130,000, many living in unlicensed camps on city outskirts.
Many Roma complain that discrimination makes it hard for them to find jobs.