Facebook has added a Finnish firm that makes a fitness tracking app to its ever-increasing portfolio of purchases.

Helsinki-based ProtoGeo created the Moves app that uses a smartphone's built-in sensors to track activity and calories burned.

The acquisition offers the social network an entry into the burgeoning health technology market.

Other recent purchases include mobile messaging firm WhatsApp and virtual headset maker Oculus.

Facebook did not reveal how much it paid for ProtoGeo, which has fewer than 10 employees, but it is believed to be a fraction of the price it has paid for more high-profile firms recently.

It paid $2bn (£1.1bn) for Oculus VR and spent $19bn (£11.3bn) on WhatsApp.