Alphabet's  (GOOG) - Get Report (GOOGL) - Get Report European antitrust headache is about to get much bigger as Brussels ramped up its case against Google's Android operating system.

The latest blow came today when the European Commission, the EU's antitrust agency, issued a formal complaint accusing Google of abusing its dominant position in Europe by imposing restrictions on Android device makers and mobile network operators.

"Today's statement of objections finds that, as a result of Google's behavior, rival search engines, mobile operating systems and web browsers have not been able to compete on their merits, but have rather been artificially excluded from certain business opportunities," EU Competition Commissioner Margrethe Vestager told journalists in Brussels. "This is worrying."

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Wednesday's accusations stem from an investigation started a year ago following complaints going back several years. They also come after the EC issued a formal complaint over Google's comparison-shopping service in a separate, still ongoing case.

In its latest complaint, the EC alleges that Google has breached EU antitrust rules on several fronts, including requiring makers of Android devices to pre-install Google Search and Google's Chrome browser and requiring them to set Google Search as the default, as a condition to license certain Google proprietary apps.

It also accuses Google of preventing manufacturers from selling smart mobile devices running on competing systems based on the Android open source code, and on giving financial incentives to device makers and mobile network operators on condition that they exclusively pre-install Google Search on their devices.

Google refuted the allegations in a statement by senior vice president and general counsel Kent Walker.

"We take these concerns seriously, but we also believe that our business model keeps manufacturers' costs low and their flexibility high, while giving consumers unprecedented control of their mobile devices," he said.

The company now has 12 weeks to respond to the EC, and can request an oral hearing. A negative decision could result in a fine of up to 10% of its global revenues, which amounted to $74.5 billion in 2015.

Much more importantly, it could be forced to change its business practices.

"In a way, the proposed fine is the least of it," said Alec Burnside, Brussels managing partner with Cadwalader, Wickersham and Taft LLP, whose firm is advising several complainants against Google, in a telephone interview.

"Google is cash-rich," he added. "The importance [of the Commission's statement of objections] is the obligation to change its ways as well as the exposure to civil liability for competition claims in the courts."

The latest case may not be the final chapter, either. Vestager said her team continues to monitor Google's behavior for other specialized search services as well as concerns relating to the copying of third-party content and advertising, signalling there may be more cases down the road.

Canada's Commissioner of Competition John Pecman yesterday pledged to keep an eye on Google even as the agency closed its investigation into several allegations of anti-competitive behavior.

In other words, Alphabet should keep its aspirin supply well-stocked.

At Wednesday morning's market open, Alphabet's stock was trading flat at $754.09 per share.