Hundreds of Instagram users have been locked out of their accounts by what appears to be Russian hackers, Newsweek reports. Users noticed that they had been logged out of their accounts when they entered the app. When they attempted to log back in, they were told that there was no account associated with the regular username, email address, or phone number.

Victims quickly realized that their account credentials had been altered, and that associated emails had been changed to a different address with a .ru suffix. They also reported profile pictures and biographies being modified (to Russian writing), although it doesn’t appear that hackers are publishing new posts.

Instagram’s security policies make it difficult for victims to regain control of their accounts, because most of their procedures require the user to be logged in. With so many affected, Instagram has been slow to respond and users have reported slow or crashing servers. Some have taken to Twitter in the hopes that they will get a response there.

According to Mashable, the affected users vary in terms of follower count. Some of the victims were Instagram “influencers” with thousands of followers. Others, however, were average users. One user who had enabled two-factor authentication (2-FA) on his account received an automated email from Instagram saying that 2-FA had been disabled.

Get the full story on Newsweek.