Stephen Elop Business Insider Nokia announced three new Android phones under the "Nokia X" brand at the Mobile World Congress in Barcelona today, a departure from its heavy reliance on Microsoft's Windows Phone 8 operating system.

The move was surprising since Microsoft is in the process of acquiring Nokia's phone and tablet business in a $7.2 billion deal that should finalize early this year.

And it's clear Microsoft isn't too happy with Nokia's decision to go Android.

When rumors started swirling about Nokia's Android phone a few weeks ago, one Microsoft insider told us the move was "embarrassing."

During a press conference at MWC Saturday, Joe Belfiore, Microsoft's corporate vice president of Windows Phone, commented on Nokia's Android devices in front of a room full of reporters and analysts.

"They'll do some things we're excited about, and some things we're less excited about," Belfiore said when asked about Nokia's Android ambitions.

Nokia's Android phones are a bit different from your typical Android phone though. The devices run heavily modified software and don't have access to Google services like Google Maps, Gmail, and the Google Play Store for apps. Instead, the Nokia X phones are packed with Microsoft services like Outlook, Skype, and the online storage service OneDrive. They'll have a separate app store for Android apps.

Nokia's former CEO Stephen Elop — who will join Microsoft once the acquisition goes through — announced the Nokia X phones today and explained that they will act as an affordable gateway to Microsoft's Windows Phones and other services. The cheapest Nokia X phone will cost about $120 U.S. and sell in "emerging markets" where most people still use regular feature phones. Nokia sees this as a good thing for Microsoft in the long run.

But there's a problem with that reasoning. Nokia already makes Windows Phones that sell for ~$100, and those devices are very popular. The Nokia Lumia 520, a budget-friendly Windows Phone, is said to be the top-selling device in its category.

Meanwhile, Microsoft's communications boss Frank Shaw wrote a carefully worded blog post saying the company is happy Nokia decided to promote Microsoft services in the Nokia X phones. But he still writes that, "our primary smartphone strategy remains Windows Phone, and our core device platform for developers is the Windows platform."

The big question on everyone's mind: Once the Nokia acquisition goes through, will Microsoft allow Nokia to continue making Android phones?