Hackers broke into the official website of a Moscow court which sentenced three Pussy Riot band members to two years in jail.
The site of the Khamovnichesky District Court was defaced with anti-Vladimir Putin slogans and a video uploaded.
In a message on the site, the attackers associated themselves with "hacktivist" group Anonymous.
"We are American group Anonymous. We don't forget and we don't forgive," said the post, in Russian.
"Justice system has to be transparent. Pussy [Riot's members] are alive," said another of the posts.
Hackers also uploaded a new song by Pussy Riot, called Putin is Lighting the Fires of the Revolution, and a video of a Bulgarian singer, Aziz.
A spokeswoman for the Khamovnichesky District Court Darya Lyakh confirmed that the site had come under a hacker attack early on Tuesday. It has now been restored and is working properly.
