At least 100,000 people have converged in Belgrade for a massive rally in the Serbian capital seen as a culmination of months-long protests against populist President Aleksandar Vucic.

Public transportation is shut down in the Serbian capital of Belgrade as tens of thousands of protesters converge to oppose Serbian President Aleksandar Vucic's government on Saturday.

The rally on Saturday in the capital, Belgrade, came as protests have spread to towns around the country and have drawn increasingly insistent calls that President Aleksandar Vucic step aside.

Calls are mounting in Serbia for an independent investigation into reports that security forces used a sonic weapon on crowd at against a huge anti-corruption rally last weekend.

Serbian officials are denying that security forces illegally used a military-grade sonic weapon to disperse and scare protesters at a huge anti-government rally