Elene Koshtaria, the leader of Georgia’s opposition party Droa, was arrested for ‘damaging’ Tbilisi Mayor Kakha Kaladze’s re-election poster.
The two men are believed to be supporters of Georgian Dream.
Megi Diasamidze was detained while traveling to visit her family in the western coastal region of Adjara.
The investigation concerns clashes between protesters and supporters of Georgian Dream in Tbilisi.
The invitation was sent in early September, less than a month ahead of election day on 4 October.
The ruling party has repeatedly denied that the OSCE would be invited to observe the elections in October.
Mamuka Khazaradze and Badri Japaridze were arrested for boycotting a controversial parliamentary commission.
