Opposition officials and human rights groups said the widely prohibited acoustic armament, which emits a targeted beam to temporarily incapacitate people, was used during the large protest over the weekend.
They have said they will file a claim with the European Court of Human Rights as well as with domestic courts in the Balkan state against those who ordered the attack.
The Serbian government denied using the weapon, and Serbian President Aleksandar Vucic on March 17 denied that the military even possessed such a weapon, in a post on Instagram.
Outgoing Serbian Prime Minister Milos Vucevic said he would be prepared to let foreign agencies from the United States and Russia investigate the allegation, telling reporters, “We are not hiding anything, we are ready to officially invite both the FBI and the FSB to come to Serbia to verify all these allegations and facts.”
The march was part of an anti-corruption movement that erupted after a concrete canopy collapsed at Novi Sad train station in the north of the country in November, causing the deaths of 15 people.
An Associated Press photographer at the rally reported people scrambling for cover, leaving the middle of the street almost empty as they fell over each other to get to the sides of an open area where they had gathered.
Those exposed to sonic weapons can experience sharp ear pain, disorientation, and panic, according to military experts, and prolonged exposure can rupture eardrums and cause irreversible hearing loss.
“This act represents a blatant display of force and an attempt to incite chaos, aiming to delegitimize protests and criminalize peaceful citizens,” the group said.
“We urge individuals of integrity within state institutions, particularly in the security sector, to refrain from complicity in mass unlawful actions against citizens.
“We demand they publicly disclose information about the weapons used, who issued the order for their deployment, and who executed it.”
Serbian police and the defense ministry denied that the weapon had been used on the protesters.
Vucic, who has been president since 2017, on March 16 urged judicial authorities to respond to the information “that sonic cannons were used during the protests,” state broadcaster RTS reported.
“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,” he said.
“Let there be a proceeding but then they should also prosecute those who went public with such a notorious lie.”
Belgrade’s emergency hospital has denied reports that many people sought help after the incident, and also called for legal action against those who “spread untrue information.”
The protesters are demanding accountability for those responsible and justice for the victims.
So far, prosecutors have charged 13 people over the disaster, and the government has announced an anti-corruption campaign.
Some of the March 15 protesters also called for a renewed general strike, though past appeals have failed to garner support among public service workers and many businesses.
