Nokia has announced at the Mobile World Congress this week that its new X, X+ and XL devices will use open versions of Google's Android mobile software systems.

The news comes just days before Nokia sells its handset business to Microsoft in deal worth $7.2 billion.

The deal was made in an attempt to "stay relevant in emerging markets," where Android phones are being purchased by hundreds of millions of people.

Nokia Chief Executive Stephen Elop said to a crowded press conference at the Mobile World Congress event that it was a move that will introduce the "next billion" users to Microsoft's services and Nokia's hardware.

"We see the X family being complementary to (Windows Phone) Lumia at lower price points," said Elop. "Even as you see Lumia push lower and lower, you will see us push lower with Nokia X below that."

The Mobile World Congress is being held in Barcelona this week.

Nokia found itself in a jam after committing to use Microsoft's Windows Phone software but still needing Android's software "to reach more cost-sensitive customers," according to CCS Insight's head of research Ben Wood.

"That a company soon-to-be owned by Microsoft, the creator of the original operating system, is moving to Android is almost an admission of failure", Wood said, according to Reuters.

The open version of Android software means new Nokia devices won't have to rely on Google's services and access to the Google Play app store. Now, Nokia is equipping the phones with its own music and map services, along with Microsoft's cloud, email, search and messaging services.

Apps will be available through Nokia's own app store, along with a number of different app stores, according to Elop.

"Lumia continues to be our primary smartphone strategy," Elop said. "Lumia is where we will continue to introduce the greatest innovation.

The 4-inch Nokia X will be available immediately, according to the company.

The X+, which has more memory and storage than the X, and 5-inch XR will be made available for purchase next quarter.

Global smartphone shipments increased to 41 percent annually to reach approximately 1 billion units in 2013, according to firm Strategy Analytics.

Android phones accounted for 781.2 million units in 2013, or almost four out of every five smartphones devices sold.

Apple sent out over 153.4 million smartphones worldwide for a 15 percent share of the market, in 2013, making it still the second largest smartphone platform, behind Android.

See Now: OnePlus 6: How Different Will It Be From OnePlus 5?