PARIS, May 13 (Reuters) - The European Commission on

Monday said it had designated Booking as a so-called

"gatekeeper" under the Digital Markets Act (DMA) while it also

opened a market investigation into social media network X to

further determine the platform's regulatory status.

Online advertising services X Ads and TikTok Ads as such did

not qualify as gatekeepers, the EU added.

The Commission said in March that Elon Musk's X, TikTok

owner ByteDance and Booking.com may meet EU criteria subjecting

them to tough tech rules as so-called gatekeepers.

While the EU on Monday said Booking qualified as a

gatekeeper, it had opened a market investigation to further

assess the rebuttal lodged by X, opposing to such a status.

ByteDance was labelled a gatekeeper in July last year but

TikTok has challenged that at Europe's second-highest court.

The Digital Markets Act (DMA) is one of the most stringent

regulations targeting large tech firms' market dominance. It

puts companies under tougher obligations to moderate content,

allow fair competition and make it easier for consumers to

switch between services.

(Reporting by GV De Clercq)