The politician arrived in Massa on Friday evening to participate in his movement's electoral campaign in the region of Tuscany. During an official appearance, a man came close to Conte pretending to want a handshake, and slapped him in the face, Italian news portal said.
The assailant then started shouting accusations against Conte for his support of lockdowns and other measures to contain the COVID-19 pandemic during his time as Italy's prime minister, according to the report.
The law enforcement officials immediately detained the assailant, Giulio Milani, 52, a known member of the no-vax movement and a candidate for the municipal elections in Tuscany, the news portal said.
"Dissent is legitimate, but this violent demonstration is outside the democratic context," Conte said after the incident, according to an Italian news portal.
Incumbent Italian Prime Minister Giorgia Meloni, as well as a number of cabinet members and politicians, expressed their solidarity with Conte.