Serbian nationalists, who want closer ties with Russia, criticize President Aleksandar Vucic for his role in talks over a Western-backed deal with Kosovo.
Both victims, aged 11 and 21, were taken to hospital following the incident on Friday, police said, adding that their injuries were not life threatening.
Kosovo declared independence from Serbia in 2008, but Belgrade has refused to recognise it and encouraged Kosovo s 120,000 ethnic Serbs to defy Pristina s authority with support from Russia
Italy s parliament gathered in joint session of both houses on Monday for the first round of voting to elect the country s new president to replace Sergio Mattarella, whose term will end on February 3.