Blizzard has confirmed that the performance of a number of its games has been disrupted by a series of distributed denial of service attacks in Europe.
The company says it's investigating an issue affecting its authentication servers, which may result in failed or slow login attempts.
"Diablo, World of Warcraft, StarCraft and Hearthstone players may be impacted by high latency and disconnections during their gaming experience that are the result of a series of DDoS attacks on certain European online services," a statement posted on Battle.net reads.
"Although Blizzard's infrastructure isn't targeted, the disruption effects rippled and have been felt by a portion of our players' population. While we are closely monitoring the situation we wanted to thank you for your patience and apologise for any inconvenience this may cause. Please follow @BlizzardCSEU_EN on Twitter for further updates."
Blizzard's latest game, Hearthstone officially launched on PC and Mac in mid-March.
At BlizzCon in November 2013, Blizzard said that the free-to-play collectible card game set in the World of Warcraft universe is also in development for iOS and Android devices.