Facebook has removed hundreds of fake Instagram accounts in Russia that were trying to interfere in the protests in the country. The company says it found a network of 530 accounts that “targeted local audiences during recent protests in support of Alexei Navalny,” the leader. Recently imprisoned Russian opposition.

Facebook says that the people behind the network have likely purchased the accounts in an attempt to bypass the social network’s automatic detection systems. The accounts in question used tactics described by Facebook as “hashtag poisoning” and “website poisoning,” which means that they mainly sent tags. Labels and website tags that protest organizers were using indiscriminately.