The right-wing protesters shouted “treason” and carried banners reading “no surrender”, as they blocked traffic before gathering near the Serbian presidential building in central Belgrade.

The protesters were also strongly pro-Russian, one banner read: “Betrayal of Kosovo is a betrayal of Russia!”

Serbian media reported that one group pushed through metal fences towards the entrance at the end of the rally but was prevented by riot police from reaching the door.

The protest comes amid efforts by US and European Union officials to mediate a solution for the long-standing dispute between Serbia and Kosovo, a former Serbian province whose 2008 declaration of independence Belgrade does not recognize.

Serbia has relied on Russia and China in its refusal to acknowledge Kosovo’s independence, which Washington and most EU countries back.

Western officials fear Moscow could use simmering tensions in Kosovo to destabilize the Balkans and avert attention away from its invasion of Ukraine.

Serbia’s populist President Vučić has said he was ready to consider the Western plan. Its provisions have not been published but it reportedly stipulates that Serbia would not object to Kosovo’s membership in international institutions, including the United Nations.

In Kosovo’s capital Pristina late Wednesday, scores of students protested peacefully against aspects of the proposed agreement with Serbia.

In Serbia, pro-Russian right-wing groups have demanded that Belgrade stop all negotiations over Kosovo but Vučić has said this would mean the end of Serbia’s integration into the EU and international isolation.

Kosovo declared independence after a war in 1998-99 that killed around 13,000 people.