Antitrust authorities in the European bloc have filed charges that could bring multibillion-dollar fines. The new case comes on the verge of a huge trial between Epic Games and Apple.

The European Commission has announced it will be pursuing Apple in an antitrust case that accuses the company of distorting the music streaming market through its App Store rules. After nearly a year of investigation triggered by a complaint by Spotify, the EU's biggest competition regulator objects to the way that Apple has assured a 30 percent cut on in-app subscription purchases.

"The Commission's preliminary view is that Apple's rules distort competition in the market for music streaming services by raising the costs of competing music streaming app developers," states a press release. "This in turn leads to higher prices for consumers for their in-app music subscriptions on iOS devices. In addition, Apple becomes the intermediary for all IAP transactions and takes over the billing relationship, as well as related communications for competitors."

If it's proved that Apple has abused its dominant market position, it could face billions of dollars — even tens of billions — in fines.

The announcement of the new case comes just days before a high-profile trial commences in Oakland, California, between Epic Games and Apple. Epic is suing Apple after trying to evade the 30 percent "tax" for purchases within Fortnite. After Epic bypassed Apple's direct payment system, Apple pulled Fortnite from its App Store. What's resulted is a closely watched case that may impact the streaming's future and feature top executives from both companies along with those at Microsoft, Alphabet and elsewhere.

The pursuit of charges also occurs as European lawmakers consider a Digital Markets Act that would enact new rules on so-called gatekeepers, including restrictions on how platforms achieve preferential treatment for their own goods.