(Bloomberg) -- Aptoide, an alternative to Google’s Play Store, said it complained to European Union antitrust regulators alleging the Alphabet Inc. unit has prevented its service from working on some users’ phones and tablets.

Aptoide said antivirus software integrated into the Android operating system thwarted users when they downloaded and tried to use the app store on their devices -- allegedly in violation of the bloc’s competition rules.

The move comes days before the EU’s antitrust authorities are set to fine Google over its conduct with Android, a case where Lisbon-based Aptoide is already one of the lead complainants. It’s unclear whether that additional complaint will fold into the EU’s existing Android probe, given the advanced stage of the investigation.

Aptoide said the Android antivirus program, Google Play Protect, was nudging users through a notification to uninstall the app store from their devices, warning them the program could download harmful apps. For those that choose to keep Aptoide despite the warning, the app store no longer functions and can’t install apps, the company said.

‘Really Aggressive’

"The behavior is really aggressive," said Aptoide CEO Paulo Trezentos, refuting the criticism that its platform is unsafe. He said Aptoide is one of the most secure app stores on the market.

Aptoide said it filed the additional complaint against Google to the European Commission, the bloc’s antitrust authority, earlier this week.

Google and the commission in Brussels both declined to comment.

On its website, Google says its built-in malware protection uses machine learning and scans billions of apps daily, both before and after installation, to ensure devices remain secure.

In a blog post in March, Dave Kleidermacher, Google’s vice president of security for Android, Play, and Chrome, said that devices that downloaded apps exclusively from Google’s own app store were nine times less likely to download a potentially harmful app than devices that installed software from other sources.

The Aptoide complaint fits into a wider battle between Google and smaller software-makers trying to carve out space on Android devices. They say Google’s conduct to impose its own apps on mobile phone and tablet manufacturers makes it hard for them to compete.

--With assistance from Aoife White.

To contact the reporter on this story: Natalia Drozdiak in Brussels at ndrozdiak1@bloomberg.net

To contact the editors responsible for this story: Giles Turner at gturner35@bloomberg.net, Peter Chapman, Nate Lanxon

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