Google said it had shipped 5 million units of the Google Cardboard viewer, a wearable device that allows users to experience virtual reality through mobile apps. Within a year and a half since its launch, 1.5 million Cardboard fans have used the device, Google said.

In the past two months (October-December), Cardboard users downloaded 10 million apps from Google Play, and they've captured more than 750,000 VR photos using the Cardboard Camera, Google added.

In total, there hae been 25 million downloads of Cardboard apps from its Google Play app store.

Google has been exploring virtual reality for a while but the company dived into the concept this month by setting up a new division for virtual reality computing.

Facebook's Oculus started accepting pre-orders this month for its Rift headset, which will ship in first quarter.

Google said in November that its video-sharing site, YouTube, supported virtual reality videos. Viewers can watch virtual reality videos using a mobile device and the Google Cardboard viewer.

Google said more than 350,000 hours of YouTube videos had been watched in virtual reality.