Russian state-owned oil company Rosneft said Tuesday that it was hit by a “massive” cyberattack on its servers.

“A massive hacker attack has hit the servers of the Company. We hope it has no relation to the ongoing court procedures,” the company tweeted, referring to ongoing litigation against Russian conglomerate Sistema. Rosneft accuses Sistema of taking $3 billion in assets from Bashneft, an oil company that Rosneft now owns.

The company told state news service TASS that the attack “could have led to serious consequences,” but it switched to a backup server system and its drilling operations have not stopped.

“Rosneft and its subsidiaries are operating on a regular basis,” press secretary Mikhail Leontyev told TASS. “Those who spread fake and panic messages will be brought to responsibility together with those who are behind the hacker attack.”

Sistema is owned by oligarch Vladimir Yevtushenkov, and the litigation is seen as part of a feud between him and Igor Sechin, Rosneft’s owner.

On Monday, a court in Russia froze Yevtushenkov’s holdings in MTS, Russia’s largest mobile operator, causing Sistema’s share value to fall