A Tbilisi office of United National Movement (UNM), a Georgian opposition party, was attacked by up to 100 masked men overnight on June 1, the party said in a statement.
UNM, founded by imprisoned ex-President Mikheil Saakashvili, is currently the strongest opposition party in the parliament and will seek to challenge the ruling Georgian Dream party in the October elections.
The news comes amid heightened tensions in the country after Georgian Dream passed a controversial "foreign agents" law, reminiscent of a similar legislation used by the Kremlin to crack down on dissent.
"The attack lasted for more than half an hour. Up to a hundred attackers took part in it," the party said on social media.
"The office's facade was damaged, glass was broken, equipment damaged."
UNM's chairman, Levan Khabeishvili, said that the assailants were armed with sticks, stones, and wooden spears.
Khabeishvili claimed that the attackers tried to get inside the building, but after the people inside resisted, the attackers fled. No injuries were reported.
UNM accused "Ivanishvili's regime" of the attack, referring to Bidzina Ivanishvili, a Georgian oligarch who is seen as the de facto leader of the Georgian Dream party.
The opposition party called the attackers "titushky," a term for hired thugs first used for violent gangs used by the Viktor Yanukovych administration during the EuroMaidan Revolution in Ukraine in 2013-2014.
Georgian activists and politicians opposing the ruling party and its "foreign agents" law complained of a growing number of threats and violent incidents targeted against them.
The Georgian Dream leadership has repeatedly denied connection to these cases and instead accused their opponents of a "hateful campaign" against the government's supporters. However, several of the party's lawmakers and pro-government figures have publicly supported the attacks against the opposition.
Violent incidents were also reportedly widespread during the anti-government protests sparked by the law's reintroduction into the parliament, with the police being accused of using rubber bullets and water cannons against the protestors.