Russia has threatened to block access to Telegram unless the company which runs the messaging app provides information about itself.

Alexander Zharov, head of communications regulator Roskomnadzor, said repeated efforts to obtain the information had been ignored and warned that "time is running out" for the app.

If Telegram hands over the details and joins Roskomnadzor's registry it would be required to keep and share users' chat histories and encryption keys with authorities if asked, according to Russian news agency TASS.

Image: Telegram provides end-to-end encryption messaging

In an open letter, Mr Zharov said: "There is one demand and it is simple: to fill in a form with information on the company that controls Telegram.

"And to officially send it to Roskomnadzor to include this data in the registry of organisers of dissemination of information."


He added: "In case of refusal…Telegram shall be blocked in Russia until we receive the needed information."

The demand is the latest standoff between the Kremlin and Nikolai and Pavel Durov, the Russian brothers who founded the end-to-end encryption app.

In 2014, the Durovs refused to comply with requests from the Russian government to turn over data on Ukranian users of Vkontakte - a social network they set up together.

Image: Telegram founder Pavel Durov and his brother have previously clashed with the Kremlin

Telegram says it splits its encryption keys into separate data centres across the globe to ensure "no single government or block of like-minded countries can intrude on people's privacy and freedom of expression".

It claims it can only be forced to hand over data if "an issue is grave and universal enough to pass the scrutiny of several different legal systems around the world".

Following the Westminster attack, Home Secretary Amber Rudd said police and intelligence agencies need access to encrypted services like Telegram and Apple's iMessage, as well as messages sent on WhatsApp.