A demonstration by Italian extreme right-wing extremists and hardcore football fans about the government's response to the coronavirus became briefly violent.
Clashes in the center of the capital, Rome, began after a fight between protesters, reports say.
The police responded with water cannons and tear gas and made several arrests.
Hundreds of people marched to ask the government to resign for having dealt with the crisis and the damage done to the economy and jobs.
With more than 33,800 deaths and 234,000 cases since the coronavirus outbreak began, Italy has been one of the hardest hit countries in the world.
Protesters gathered in the old area around Circus Maximus.
The clashes started when one of his representatives started talking to the media, the reports say.
Some protesters threw bottles, stones and smoke bombs at police, journalists and photographers and shouted "journalists, terrorists", the AFP news agency reported.
One protester said the participants were people who wanted to restore "legality and dignity in Italy".
"We are here to make the whole world understand that today in Italy all categories of workers are devastated and destroyed by a government that is in fact not in the interests of Italians," he told Reuters news agency.
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Italy has entered its final phase, easing blocking restrictions, allowing domestic travel between regions and opening its international borders.
Prime Minister Giuseppe Conte said the government is working to accelerate social payments and has promised "a serious tax reform".
Shops, cafes and restaurants had already opened their doors again, and tourist attractions began to receive tourists in the past few days.