Russia's state media regulator has asked a court to block the messaging app Telegram following the company's refusal to give the Federal Security Service (FSB) access to users' messaging data.

In a statement on its website, Roskomnadzor said it had filed suit with Moscow’s Taganka district court on April 6 seeking "restrictions on access to...Telegram on the territory of Russia."

The move may fuel concerns that Russia is seeking to curtail Internet freedoms following President Vladimir Putin's March 18 election to a new six-year term.

On March 20, Roskomnadzor ordered Telegram to provide the FSB with encryption keys needed to read users' messaging data within 15 days, after the Supreme Court rejected Telegram's challenge to the demand.

Telegram has been defiant. Co-founder Pavel Durov, who lives in self-imposed exile abroad, said after the Supreme Court ruling that his company would not provide the FSB with encryption keys.

"Threats to block Telegram unless it gives up private data of its users won't bear fruit. Telegram will stand for freedom and privacy," Durov wrote on Twitter at the time.

Kremlin critics have used social media to spread the word about antigovernment demonstrations and to publicize corruption allegations against Putin, a former FSB chief and Soviet KGB officer, and his allies.