Rome, like many European capitals, has ramped up security since the Nov. 13 attacks that killed 130 people in Paris.
There have been isolated episodes of violence toward immigrants around Italy and right-wing politicians have called on the country`s Muslims to show their rejection of militancy.
"These terrorist groups are only creating hate between peoples and between religions," said Mustapha Hajraoui, president of the Italian Islamic Confederation.
"We are here to say `no` because our religion is not a religion of terrorism, it is not a religion of war but of peace and coexistence."
Marchers chanted "no to terrorism", held placards saying "terrorism is a cancer" and "we are not the enemy", and listened to a message of support from Italian President Sergio Mattarella.
Numerous Italian politicians attended the event, including Khalid Chaouki, a deputy of Moroccan origin from the governing Democratic Party, who has been put under police protection due to repeated threats against him since the Paris attacks.
Similar rallies were held in Milan and Genoa.
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