France's competition regulator on Monday fined Google 220 million euros ($267 million) after finding it had abused its dominant market position for placing online ads, the latest move by European authorities to take tougher stances against US tech giants.

The penalty is part of a settlement reached after three media groups -- News Corp, French daily Le Figaro and Belgium's Groupe Rossel -- accused Google of effectively having a monopoly over online ad sales.

The Autorite de la Concurrence determined that Google gave preferential treatment to its own ad auction service AdX and Doubleclick Ad Exchange platform, a real-time auction platform.

Clients trying to place ads on internet sites or mobile apps using rival platforms often found they were paying more than those using both of Google's services, since regrouped under the Google Ad Manager brand.

The regulator said Google did not contest its findings and has committed to operational changes including improved interoperability with third-party ad placement providers.

"It is the first ruling in the world to scrutinise the complex algorithmic processes for the auctions that determine online 'display' advertising," the authority's president Isabelle de Silva said in a statement.