People with banners and flags, chanting "Free Palestine" and other slogans, filed past the Colosseum, taking part in a march that organisers said attracted more than one million people, while police put the figure at around 250,000.
"I'm here with a lot of other friends because I think it is important for us all to mobilise individually," said Francesco Galtieri, a 65-year-old musician from Rome. "If we don't all mobilise, then nothing will change."
The protest, in bright sunshine, was peaceful, with students, children, and the elderly attending. It also featured at least one banner hailing Hamas' October 7 attack on Israel, and anti-Israeli chants.
As the march was ending, around 200 people broke away and clashed with officers in riot gear near the St. Mary Major basilica, police said. Officers responded with tear gas and a water cannon.
Protesters threw Molotov cocktails and set fire to a police car, the AGI news agency said. Earlier, a Reuters witness saw police immobilise, handcuff, and take away some of the suspected rioters.
Since Israel started blocking the flotilla late on Wednesday, protests have sprung up across Europe and in other parts of the world, but in Italy, they have happened daily, and in multiple cities.
On Friday, unions called a general strike in support of the flotilla, with demonstrations across the country that attracted more than two million people, organisers said. The Interior Ministry estimated attendance at around 400,000.
Italy's right-wing government has been critical of the protests.
Prime Minister Giorgia Meloni on Saturday blamed protesters for insulting graffiti that appeared on a statue of the late Pope John Paul II outside Rome's main train station, where pro-Palestinian groups have been holding a protest picket.
"They say they are taking to the streets for peace, but then they insult the memory of a man who was a true defender and builder of peace. A shameful act committed by people blinded by ideology," she said in a statement.
Israel launched its Gaza offensive after Hamas militants staged a cross-border attack on October 7, 2023, killing some 1200 people and taking 251 people hostage, according to Israeli tallies.
Since then, Israel's offensive has killed more than 67,000 Palestinians, according to Gaza health authorities, and exposed Israel to accusations of genocide, which the country has strongly rejected.
