By Dave Sebastian

The developer of the science-fiction action game "Cyberpunk 2077" said its internal systems were breached in a cyberattack and has declined to pay a ransom to retrieve compromised data.

CD Projekt SA on Tuesday said an unidentified hacker accessed its internal network and collected certain data belonging to its capital group. The company said it has begun restoring the data and that its backups remain intact. The compromised systems didn't contain personal data of its players or users of its services, the Warsaw-based company said.

The hacker left a ransom note in CD Projekt's system, the company said. In the undated note, a copy of which CD Projekt posted on Twitter, the hacker threatened to sell or leak source codes for the company's popular videogames and internal documents if the company didn't come to an agreement with the hacker. The hacker gave the company 48 hours to contact them, according to the note.

"We have dumped FULL copies of the source codes from your Perforce server for Cyberpunk 2077, Witcher 3, Gwent and the unreleased version of Witcher 3!!!" the note said. "We have also dumped all of your documents relating to accounting, administration, legal, HR, investor relations and more!"

The company said it has approached authorities including law enforcement and Poland's president of the Personal Data Protection Office.

"We will not give in to the demands nor negotiate with the actor, being aware that this may eventually lead to the release of the compromised data," CD Projekt said. "We are taking necessary steps to mitigate the consequences of such a release, in particular by approaching any parties that may be affected due to the breach."

CD Projekt shares fell about 5% in Warsaw trading.

The cyberattack is the latest issue facing the videogame developer whose reputation has been dented by the rocky rollout of its most ambitious project "Cyberpunk 2077."

The company is in the midst of overhauling the game, which after its release in December contained glitches that led a deluge of player complaints and prompted the company to offer refunds. Sony Corp. pulled the game in December from its PlayStation Store amid the complaints.

Write to Dave Sebastian at dave.sebastian@wsj.com

(END) Dow Jones Newswires

02-09-21 0928ET