Serbian President Aleksandar Vucic condemned efforts by the Russian Wagner Group in his country to recruit fighters, after the group published a local advertisement calling on Serbs to fight in Ukraine.
The position of the Serbian president includes a rare public criticism of Russia, from a country in the Balkans that is classified as an ally of Moscow.
The "Beta" news agency quoted Vucic as saying in a televised interview, "Why are you doing this to Serbia? Why did Wagner make an illegal call?"
The Serbian branch of the Russian-backed RT broadcaster aired the controversial ad earlier this month.
A small number of Serbs have been fighting alongside Moscow-backed forces in Ukraine since fighting broke out in the country for the first time in 2014. The Serbian authorities have not published any specific number for the number of Serbs who have fought in Ukraine.
Serbia has long been a reliable ally of Russia, and with the exception of Belarus, Serbia is the only European country that has not followed the example of the West in imposing sanctions on Moscow.
On Tuesday, the Russian news agency "RIA" broadcasted scenes apparently showing two Serbian citizens taking part in weapons training in Ukraine.
The Wagner Group - founded in 2014 and involved in several conflicts in Africa and the Middle East - emerged after Russian President Vladimir Putin ordered his forces to wage war on Ukraine on February 24, 2022.
Since the start of the war, tens of thousands of Russians have moved to Serbia, and despite the arrival of Russian opponents to Serbia to escape the war, the majority of Serbs still support the war on Ukraine, and demonstrations in support of the Kremlin were organized in Belgrade.