Russia's telecoms watchdog on Friday asked a Moscow court to block the popular messaging app Telegram, after a deadline for it to hand over encryption keys to security services expired.

Roskomnadzor said in a statement it had filed a lawsuit "demanding the limiting of access on Russian territory" to encrypted app Telegram.

Telegram's self-exiled Russian founder Pavel Durov has long said he will reject any attempt by the country's security services to gain backdoor access to the app.

The free instant messaging application, which lets people exchange messages, photos and videos in groups of up to 5,000 people, has attracted more than 200 million users since its launch in 2013.

Telegram is especially popular among political activists of all stripes, but has also been used by jihadists.

It comes after Iran reportedly moved to block the app on Saturday after a series of protests earlier this year believed to have been organised through the platform.

In September 2017 the FSB security service demanded encryption keys, Durov said, prompting a formal complaint when the request was rejected.

Durov wrote last year that the FSB's demands are "technically impossible to carry out" and violate the Russian Constitution which entitles citizens to privacy of correspondence.