The FSB has revealed signs of a staged provocation in the protest in Belgrade

Russia's Federal Security Service (FSB) has revealed signs of a staged provocation involving a specially trained group of individuals at a March 15 protest in Belgrade. The document with the results of the investigation was published on the website of the Serbian Security and Information Agency (BIA).

FSB experts also denied reports of the alleged use of a "sound cannon" by Serbian law enforcement agencies.

"There are clear signs of a staged provocation involving a specially trained group of individuals and the use of smartphones to synchronize movement while simulating the effect of an acoustic cannon, as well as blocking an ambulance," the document says.

Interviewed law enforcement and medical personnel who attended the rally reported that they did not hear unusual sounds and did not observe the physiological effects characteristic of a "sonic cannon."

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On March 29, Serbian President Alexander Vucic announced that representatives of the Russian FSB had launched an investigation into the possible use of a "sound cannon" during the protests in Belgrade on March 15. The Serbian president explained that the FSB officers would help show how those accusing the government of using a "sound cannon" mislead the population.

Earlier, on March 19, Vucic announced that he would resign if information about the use of a "sound cannon" by police officers at protests in Belgrade was confirmed.