Former Philippine president Rodrigo Duterte's arrest has sparked protests from his supporters, including in front of the International Criminal Court in the Dutch city of The Hague where he faces crimes against humanity charges.

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.

Hundreds of thousands of people descended on Serbia's capital on Saturday to protest over the deaths of 15 people in a railway station collapse. While the government put attendance at 107,000 across Belgrade, an independent monitor said 325,000 - if not more - had gathered, making it Serbia's largest protest ever.

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