The hackers claimed to have downloaded source code for video games such as FIFA 21 and for the proprietary Frostbite game engine used as the base for many other high-profile games at Electronic Arts (EA).
News of the hack was first reported by news site Vice, which said some 780GB of data was stolen.
The Electronic Arts (EA) said no player data had been stolen in the breach.
The firm is one of the largest games companies in the world. It counts major series such as Battlefield, Star Wars: Jedi Fallen Order, The Sims, and Titanfall among the titles it develops or publishes – as well as a vast array of annual sports games.