VKontakte facing legal action from record labels
Social network VKontakte (VK) - dubbed the "Facebook of Russia" - is facing legal action from the recording industry.
Sony, Universal and Warner Music have each filed a case accusing the site of "large-scale" copyright infringement.
The action has been coordinated by the International Federation of the Phonographic Industry (Ifpi), which represents record labels worldwide.
VK has not responded to the BBC's request for comment.
The labels have accused VK, the second biggest social network in Europe, of creating a "huge library" of music it does not have the rights for and offering it as a service within its site.
The labels are seeking a court order in Russia to make VK to remove a number of files from its service.
In a statement announcing the action, Ifpi chief executive Frances Moore said:"We have repeatedly highlighted this problem over a long period of time.
"We have encouraged VK to cease its infringements and negotiate with record companies to become a licensed service.
"To date the company has taken no meaningful steps to tackle the problem, so today legal proceedings are being commenced."'Notorious'
The labels argue that the popularity of VK, and the existence of the music library, make it difficult to set up a legal service in Russia.
"This is an action which can benefit the whole music industry in Russia," said Leonid Agronov, chief executive of the National Federation of the Music Industry, a Russian trade body for the recording industry.
VK has been on the radar of copyright holders for some time - the US Trade Representative's annual report into "notorious markets" has highlighted VK as a problem for the past four years.
In November 2012, VK was found guilty by the Russian Supreme Court of distributing unlicensed music belonging to the Gala Music Group.
That decision followed Russia's joining of the World Trade Organisation - a requirement of which was to tighten up its copyright laws and enforcement.
This latest action comes at a time of instability at VK.
On 1 April, the site's founder, Pavel Durov, announced he was to leave the company, but later rescinded his resignation - suggesting it was an April Fool's joke.
His resignation note - even if a prank - touched on a delicate issue for VK. Recent shareholder changes have led many to suggest the site is now closely controlled by the Kremlin, and has been under pressure to remove posts supporting Ukraine.