New York, Jan 2 (IANS): As an earlier statement said WhatsApp will stop working on certain phones by the end of 2016, many users of older versions of iPhones and Android handsets are about to find themselves cut off from using the chat app, media has reported.

WhatsApp, with more than one billion monthly users, had earlier announced that it was phasing out compatibility with older phones in a technology upgrade.

According to a report in the Independent on Monday, WhatsApp said that the move had been made to ensure that the app could continue to introduce new features and stay secure, which relies on the app being used on newer operating systems.

In the developing markets where the chat app and older phones are popular, WhatsApp has faced a sharp criticism for its move.

WhatsApp had initially listed all BlackBerry models and some Nokia handsets among the handsets that would be blocked from the chat app. However, the company retracted late last year, apparently in response to complaints.

"We are extending support for BlackBerry OS, BlackBerry 10, Nokia S40 and Nokia Symbian S60 until June 30, 2017," WhatsApp wrote in an update to its blog.

The service will stop on any first, second, third or fourth generation iPad that has not been updated. Users need to update to iOS 9.3 to use the service.

With these changes, WhatsApp is expected to more deeply integrate encryption and other privacy services.

"Such technology stops messages from being read, and has led to WhatsApp facing criticism from governments who believe that WhatsApp conversations should be made public," the report added.