By Andrew Osborn and Polina Devitt

MOSCOW (Reuters) - President Vladimir Putin ordered the suspension of all Russian passenger flights to Egypt on Friday until the cause of a deadly plane crash at the weekend was established.

Putin's decision was a response to the unexplained crash of an Airbus A321 operated by a Russian carrier on Saturday over Egypt's Sinai Peninsula. All 224 people on board were killed.

The move, which follows decisions by Britain and Ireland to suspend flights to and from Sharm al-Sheikh, the Egyptian resort where the downed Russian airliner originated, is the first sign that Moscow is attaching credibility to the theory that Islamist militants somehow planted a bomb on the aircraft.

Putin acted after Alexander Bortnikov, the head of Russia's FSB security service, recommended that Russia suspend all passenger flights to Egypt until it knew exactly what caused the crash.

"The head of state agreed with these recommendations," Dmitry Peskov, Putin's spokesman, was quoted as saying by the Interfax news agency.

"V. Putin has tasked the government with working out a mechanism to realise the recommendations of the National Anti-Terrorism Committee and to ensure the return of Russian citizens to the motherland."

Putin had also ordered the government to open talks with Egyptian authorities to guarantee the safety of flights, said Peskov.

A Sinai-based group affiliated with Islamic State, the militants who have seized swathes of Iraq and Syria, has claimed responsibility for the crash, which, if confirmed, would make it the jihadist organisation's first attack on civil aviation.

But before Friday afternoon, the Kremlin had firmly said it was too early to say what caused the crash and that all theories, including the possibility of technical failure, should be examined by the official investigation.

Britain and Ireland have already suspended regular flights to Sharm al-Sheikh amid growing concerns over what caused the plane crash and the level of security at the resort's airport.

Egypt is one of the most popular holiday destinations for Russians and any decision to suspend flights would cause major logistical problems for Russia's airlines and stranded tourists.

(Reporting by Polina Devitt, Denis Dyomkin and Andrew Osborn; Editing by Christian Lowe)