Russian oil giant Rosneft says a "powerful" hacking attack has been carried out against its servers.
In a June 27 statement, the state-owned company expressed hope that the incident was "not connected to current legal proceedings."
It said "neither oil output nor refining have been stopped" due to the attack.
Earlier this year, Rosneft filed a multibillion-dollar lawsuit against business conglomerate Sistema.
Rosneft claims that Sistema removed assets from oil company Bashneft when the latter was owned by Sistema and prior to Rosneft taking a controlling stake in the company in October 2015.
Sistema has denied the claim has any foundation.
