Apple reversed course on Friday and will allow Epic Games to develop a competing European app store for iPhones after a feud between the two companies tested a new law governing big tech on the continent.

"Following conversations with Epic, they have committed to follow the rules, including our DMA policies," an Apple spokesperson said in an email to AFP.

"As a result, Epic Sweden AB has been permitted to re-sign the developer agreement and accepted into the Apple Developer Program," the spokesperson added.

Apple was referring to the Digital Markets Act, a landmark European law that came into force on Thursday and orders the world's biggest tech companies to open up their platforms to competition.

Six of the biggest companies designated as "gatekeepers" had until the end of Thursday to comply with tough new DMA rules.

Epic CEO Tim Sweeney called the turnaround "a big win for European rule of law, for the European Commission, and for the freedom of developers worldwide to speak up."

The maker of Fortnite earlier in the week told the EU commission that its effort to build an app store for its video game empire had been rejected by Apple.

Specifically, Apple on March 2 closed Epic's Sweden-based developer account that allowed it to build the software necessary to launch its standalone stores on Apple devices in Europe.

Sweeney had compared Apple's actions to "feudal lords mounting the skulls of their former enemies on their castle" in an effort "to dissuade others" from speaking out.

Epic Games has been in Apple's and Google's crosshairs for years over access to the app store.

The game maker turned to courts and regulators to demand that Apple and Google open up their iPhone and Android devices to competing app stores and stop taking hefty fees for purchases made on their devices.

Those demands were included in the DMA's long list of do's and don'ts for the gatekeepers that came into force on Thursday.

"I take note with satisfaction that following our contacts Apple decided to backtrack its decision on Epic exclusion. From Day 2, #DMA is already showing very concrete results!" the EU's internal market commissioner Thierry Breton said.