A jury in the United States has found that Google unlawfully made its Play Store dominant over rival app stores.

Epic Games, which owns popular video game Fortnite, sued Google in 2020, accusing it of a monopoly over the distribution of apps and in-app billing.

Hundreds of millions of people globally use the store to install apps for smartphones powered by Google's Android software.

Google said it would challenge the outcome.

"Android and Google Play provide more choice and openness than any other major mobile platform," Wilson White, vice-president of government affairs and public policy at Google, said.

"The trial made clear that we compete fiercely with Apple and its App Store, as well as app stores on Android devices and gaming consoles.

"We will continue to defend the Android business model and remain deeply committed to our users, partners, and the broader Android ecosystem,"

Epic Chief Executive Tim Sweeney said that work on remedies would start in January.

"Victory over Google! After 4 weeks of detailed court testimony, the California jury found against the Google Play monopoly on all counts," Epic Chief Executive Tim Sweeney wrote in a post on X, formerly known as Twitter.

The lawyers for the two companies made their final arguments on Monday in the trial that lasted more than a month.

The case also challenged transaction fees of up to 30% that Google imposes on Android app developers.

Epic said in the lawsuit that Google "suppresses innovation and choice" through a "web of secretive, anticompetitive agreements".

Google had countersued for damages against Epic for allegedly violating the company's developer agreement.

The tech giant has faced a number of anti-trust cases, settling similar claims from dating app Match before the Epic trial started.

Epic filed a similar antitrust case against Apple in 2020, but a US judge largely ruled in favour of Apple in 2021.