Social network Strava released a heatmap visualising users' activity around the world

A map made from data logged on a fitness tracking app appears to highlight activity around secretive locations such as military bases.

Strava is a 'social networking' website & app aimed at athletes, and allows users to upload data from devices such as Fitbits.

The company released a global heatmap in November, visualising data from users' activities such as running and cycling.

While most activity is centered around cities and other population centres, concerns were raised over the weekend that anyone browsing the maps could clearly identify specific tracks around various military bases and centres around the world.

Nathan Ruser, an analyst with the Institute for United Conflict Analysts, observed: "If soldiers use the app like normal people do, by turning it on tracking when they go to do exercise, it could be especially dangerous."

In a statement quoted by CNN, Strava said: "Our global heatmap represents an aggregated and anonymised view of over a billion activities uploaded to our platform. It excludes activities that have been marked as private and user-defined privacy zones.

"We take the safety of our community seriously and are committed to working with military and government officials to address sensitive areas that might appear."