Calls were mounting in Serbia on Monday for an independent investigation into reports that security forces used a prohibited sonic weapon on crowds at a huge peaceful 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.

The incident left 15 people dead, with protesters blaming President Vučić’s government, alleged corruption, and a lack of safety regulations. Reports in Serbian media said 22 people were arrested and 56 were injured during the protests.