Tensions were rising in Serbia days ahead of a mass anti-corruption protest as ultranationalist backers of the government flocked to the capital, sparking concerns of a confrontation between the rival camps.

Several hundred students have blocked Serbia’s public television station building in Belgrade as tensions soar in the Balkan country days ahead of a planned large rally billed as an endgame in months of massive anti-government protests.

Anti-government protesters barred access to the offices of state broadcasters in Serbia's capital Belgrade and the second-largest city on Tuesday, keeping employees out and forcing some live programming off the air.

Serbian protesters blocked offices of the state broadcaster in the capital and second-largest city Novi Sad overnight, in a bid to draw attention to their months-long rallies against the rule of President Aleksandar Vucic.