Novak Djokovic courted controversy Monday when he wrote “Kosovo is the heart of Serbia. Stop the violence" on a camera at the French Open after clashes flared in northern Kosovo amid ethnic tensions.

The Belgrade-born tennis superstar wrote the message in Serbian after his opening round victory over Aleksandar Kovacevic on the showpiece Philippe Chatrier Court at Roland Garros.

“Kosovo is our cradle, our stronghold, centre of the most important things for our country. There are many reasons why I wrote that on the camera," 36-year-old Djokovic told Serb media at the tournament.

NATO-led peacekeepers on Monday dispersed Serb protesters who again clashed with police in northern Kosovo to demand the removal of recently elected Albanian mayors, as ethnic tensions flared in the Balkan nation.

Around 25 soldiers were injured during the clashes, along with over 50 demonstrators.

Kosovo’s Serbs had boycotted last month’s elections in the northern towns, which allowed ethnic Albanians to take control of local councils despite a minuscule turnout of under 3.5 percent of voters.