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.

Serbian officials denied Sunday that the country's security forces used a military-grade sonic weapon to disperse and scare protesters at a huge anti-government rally in the capital. Rights groups claimed that the widely banned acoustic weapon was used during the protest Saturday.

Tens of thousands of people have descended on Serbia's capital to protest against the deaths of 15 people in a railway station collapse. The government has put attendance at 107,000 across Belgrade. Organisers and independent monitors have yet to give their estimates.