Serbian authorities have denied that the country’s security forces used a military-grade sonic device to disperse and scare peaceful protesters at a major anti-government rally over the weekend.

They say that such acusations are “blatant lies” amplified by a Soros and USAID-funded NGO.

Authorities in Belgrade have now called for an investigation into those responsible for spreading misinformation after opposition leaders and a foreign-funded NGO accused security forces of using sound cannons against the protesters.

Reports say that between 325,000 to over a million people took part in an anti-government protest on Saturday, which has described as one of the largest in Serbia’s recent history.

In a social media post on Sunday, Serbian president President Aleksandar Vucic claimed the demonstrations were politically motivated aimed at destabilizing Serbia. He denied that authorities had used any form of sonic weaponry.

So what exactly happpened?

RT reports: Videos from the rally show protesters reacting to a sudden whooshing sound, triggering a brief stampede as the crowd moved away from the center of the road. However, the demonstrators soon returned, visibly puzzled but seemingly unharmed.

The opposition Freedom and Justice Party (SSP) accused security forces of deploying a Long Range Acoustic Device (LRAD), a crowd-control sound cannon that emits high-frequency sounds exceeding 160 decibels and can cause pain and disorientation.

The Belgrade Centre for Security Policy (BCSP), a Soros-backed and USAID-funded non-governmental organization, issued a statement on Sunday condemning “the unlawful and inhumane deployment of prohibited weapons, such as acoustic devices, against peaceful protesters.”

The Serbian authorities have denied using any form of sonic weaponry. The Ministry of Internal Affairs stated that there is no evidence to support the claims, calling them “an attempt to destabilize the country.” Government officials insist that law enforcement acted within the law and maintained order without excessive force.

Addressing the public on Saturday, President Aleksandar Vucic dismissed the opposition’s accusations, saying a real sonic cannon “beeps so eerily, it causes such nausea and vomiting that you can’t recover from it for days.”

“Just so you know what kind of lies we’re talking about… I am asking the Ministry of Justice and the prosecutor’s office to react – either to prosecute those who used it, and we know they didn’t, but let’s check,” Vucic said on Sunday.

“Let there be a proceeding, but then they should also prosecute those who went public with such a blatant lie.“

An emergency hospital in Belgrade denied reports that large numbers of people sought medical assistance after the incident, also urging legal action against those who “spread untrue information.”