Google’s new video calling app Duo, launched last week, reached 5 million downloads by Android users, the tech giant’s CEO Sundar Pichai said.

It also appears in the most popular apps list in Google Play Store.

The app was launched to rival Apple’s FaceTime, Facebook Messenger and Skype. Unlike FaceTime though, Duo is available for both Android and iOS users, although there is no word yet on how many iOS downloads it has garnered.

It is currently number 14 in the UK App Store’s free social networking apps list.

Google has been keen to talk up the app’s simplicity, as it only requires a phone number to be used, and not a separate account.

Duo is optimised to connect video calls even when users are on slower networks, to address failed and dropped calls, with the capability to switch between Wi-Fi and mobile data.

With “an emphasis on privacy and security”, all Duo calls are also end to end encrypted.

Perhaps a big differentiator from FaceTime, Duo also supports a feature called Knock Knock, which enables users to see live video of the caller before answering, “giving you a sense of what they’re up to and why they want to chat”.

At its I/O developer conference, the company also announced Allo, an instant messaging app, which is yet to be released.