The mayor of an Armenian town affiliated with the former ruling Republican Party (HHK) and four other men have been arrested on suspicion of assaulting protesters in Yerevan last month.

The incident took place in the city’s southern Erebuni district just hours after Nikol Pashinian, the main organizer of mass protests against HHK leader Serzh Sarkisian’s continued rule, was detained on April 22. Hundreds of Pashinian supporters demonstrating there were attacked by several dozen men wearing medical masks and wielding sticks and even electric shock guns. They threw stones at the crowd and beat up some of the protesters.

Law-enforcement authorities launched a criminal investigation into the attack after Sarkisian resigned as prime minister on April 23. Pashinian demanded such a probe immediately after being elected as the country’s new premier on May 8.

Armenia’s Investigative Committee said on Thursday that it has arrested five persons on suspicion of participating in the “mass disturbances” in Erebuni. It said they include Davit Hambardzumian, the mayor of Masis, a small town about 10 kilometers south of Yerevan, his deputy Karen Ohanian and three other Masis residents.

The law-enforcement body said its investigators have looked into online videos of the violence and other media reports about it. “The investigation is continuing,” it said in a statement. “Measures are being taken to ensure a comprehensive, full and objective examination of all circumstances of the incident.”

A screenshot of one such video publicized by the “Haykakan Zhamanak” daily purportedly shows that Hambardzumian was among the masked thugs who attacked the protesters in Erebuni.

It was not immediately clear whether the Masis mayor and the other detained men admit their involvement in the attack.

Hambardzumian, 32, is an HHK member who was elected mayor in 2016 with the help of the then ruling party. He is reportedly related to Arshak Hakobian, the chief bodyguard of Vladimir Gasparian, the former chief of the Armenian police sacked by Pashinian earlier this month.

Law-enforcement authorities have also made at least three other arrests in connection with similar incidents that occurred in two other parts of Yerevan during the Pashinian-led protest movement. Some Armenian media outlets have accused Yerevan Mayor Taron Markarian and Mihran Poghosian, a controversial parliamentarian, of orchestrating those attacks on protesters. Both men affiliated with the HHK deny that.