Hackers staged a surprise attack on the online role-playing game World of Warcraft and "killed" some virtual characters, the company operating the game said Monday.
"Earlier today, certain realms were affected by an in-game exploit, resulting in the deaths of player characters and non-player characters in some of the major cities," said a blog post by site manager "Nethaera" on Warcraft, which is owned by Blizzard Entertainment.
"This exploit has already been hotfixed, so it should not be repeatable. It's safe to continue playing and adventuring in major cities and elsewhere in Azeroth."
The posting said that "we are taking this disruptive action very seriously and conducting a thorough investigation."
The company apologized to users and asked anyone with information to contact the firm.
The attack apparently began Sunday, according to members of the online forum WoW Insider.
"Something very strange happened on various realms," Olivia Grace wrote on the forum, adding that "everyone in Stormwind and Orgrimmar was killed... It's also been happening on Tarren Mill, Ragnaros, Draenor, Twisting Nether, and no doubt other servers."
Around 10 million people worldwide pay subscription fees for the game including several million who have joined the most recent campaign, "the fight for Pandaria."
Players represented by animated characters such as dwarfs, trolls, or humans explore, battle, and take on quests in the game made by Blizzard, a division of Activision.
Explore further: Britain threatens Internet 'trolls' with two years in jail