Russia has threatened a ban against Telegram end-to-end encrypted messaging app, after Pavel Durov, its founder, refused to sign up to the country's new data protection laws.

Russia's FSB intelligence service said on Monday that the terrorists who killed 15 people in Saint Petersburg in April had used the Telegram encrypted messaging service to plot the attacks.

According to the new Russian Data Protection Laws, since January 1, all foreign tech companies have been required to store past six months' of the personal data of its citizens and encryption keys within the country; which the company has to share with the authorities on demand.

"There is one demand, and it is simple: to fill in a form with information on the company that controls Telegram," Alexander Zharov said, head of communications regulator Roskomnadzor (state communications watchdog).

"And to officially send it to Roskomnadzor to include this data in the registry of organizers of dissemination of information. In case of refusal… Telegram shall be blocked in Russia until we receive the needed information."

Russian wants Telegram to share its users' chats and crypto keys if asked, as the encrypted messaging app has become widely popular among terrorists for operating inside Russia.

Founder Pavel Durov said on Twitter that Intelligence agencies had pressured the company to weaken its encryption or install a backdoor.

So far, Telegram has refused to comply with the requirements in order to protect the privacy of its more than 6 million Russian users.

November last year, LinkedIn, the world's largest online professional network, was also banned in Russia for not complying with the country's data protection laws.