Messaging app WhatsApp has hit 400 million monthly active users, with Jan Koum, the company’s CEO, noting that this is “a milestone that no other mobile messaging service has achieved”.

Noting that the figure is the number of people actively using the app each month, rather than a count of registered users, the executive said that the company has added 100 million users in the last four months alone.

The former point appears to be a swipe at rivals such as LINE and Kik, which in recent weeks have released registered user numbers.

Indeed, following the 20 million downloads BlackBerry saw of its BBM app for Android and iOS following launch, Andrew Bocking, EVP of BBM for BlackBerry, said that moving forward “we will focus on active users of BBM and will no longer focus on simple download numbers”.

Koum wrote: “WhatsApp has just 50 employees, and most of us are engineers. We’ve arrived at this point without spending a dollar on targeted ads or big marketing campaigns.”

Late last month, the company introduced an app targeting users of Nokia’s mass-market Asha devices.

WhatsApp has also recently inked partnerships with operators Tata Docomo and Vimpelcom.