Facebook has bought the fitness app Moves, which helps users monitor physical activity and their calorie counts on a smartphone. Finnish startup ProtoGeo, which developed the app, said Thursday it had been acquired by the US social networking giant for an undisclosed amount, and that key members of its team would be moving to the Facebook headquarters in Menlo Park, California.

Facebook did not disclose the price it paid for ProtoGeo Oy

Both companies said Moves would continue as a standalone application, rather than be integrated into the Facebook framework.

"The Moves team has built an incredible tool for the millions of people who want to better understand their daily fitness activity, and we're looking forward to the app continuing to gain momentum," Facebook said in a statement.

Fitness tracking is attracting the attention of large and small technology companies.

Facebook made two large acquisitions earlier this year, spending $19 billion for the instant messaging service WhatsApp and $2 billion for a virtual reality company, Oculus.