Anticipating protests during the Turkish leader’s visit, Italian authorities enforced a 24-hour ban on protests in central Rome from Sunday night to Monday.
The order was ignored by a pro-Kurdish group, which objects to Turkey’s treatment of Kurds in Turkey and Syria.
The protesters held a sit-in outside Castel Sant’Angelo, not far from where Mr Erdogan was scheduled to meet with Pope Francis at the Vatican.
The demonstrators, carrying a banner reading “Erdogan killer” and chanting “shame, shame”, attempted to march towards St Peter’s Square, but were blocked by police dressed in riot gear and armed with batons.
Two people were arrested and two injured.
“So much for your democracy,” one protester told ANSA.
“Today we’re here to defend our mothers and children. Today you and the pope lost.”
Mr Erdogan met Pope Francis for just under an hour on Monday morning, discussing the status of Jerusalem and tensions in the Middle East, as well as the challenges facing Turkey as it takes in vast numbers of refugees.