The UK antitrust regulator has blocked Microsoft's $69 billion purchase of Activision Blizzard over competition concerns.

The Competition and Markets Authority "has prevented Microsoft's proposed purchase of Activision over concerns the deal would alter the future of the fast-growing cloud gaming market, leading to reduced innovation and less choice for UK gamers over the years to come," the regulator said in a statement Wednesday.

— This is a developing story and will be updated.