The Airbus 321-200, carrying mostly Russian citizens, was returning to Saint Petersburg in Russia from the city of Sharm al-Sheikh, a popular Egyptian Red Sea resort, Egyptian authorities said Saturday.

Egypt's Foreign Minister Sameh Shoukry called his Russian counterpart on Saturday with his condolences and also to express Cairo's commitment "to uncover the circumstances surrounding the incident, in full cooperation and coordination with the Russian side."

The aircraft was in the air for only 23 minutes before crashing in a mountainous region of the Sinai Peninsula.

"I now see a tragic scene," an Egyptian security officer at the site told the Reuters news agency.

"A lot of dead on the ground and many who died whilst strapped to their seats. The plane split into two, a small part on the tail end that burned and a larger part that crashed into a rock. We have extracted at least 100 bodies and the rest are still inside," said the officer who requested anonymity.

There were no survivors from the crash, Egyptian officials and the Russian embassy in Cairo said.

There were 24 children on board the Airbus, according to ATOR, the association of Russian tourist agencies.

Pilot reported problems

The Egyptian investigators found one of the plane's two flight recorders or "black boxes," at the scene.

A senior, Egyptian, air traffic controller said that the plane's pilot told him in his last transmission that he was having trouble with the radio system.

The pilot also reportedly said he wanted to make an emergency landing, before losing contact with ground control.

The initial information suggests that the plane crashed due to a technical fault, security sources in North Sinai said.

Mourning in St Petersburg

The 18-year old Airbus went through a detailed check last year, according to the TH&C Holding company which owns the Kogalymavia airlines which operated the flight.

Authorities in both Russia and Egypt have started investigations into the incident. Moscow will "insist" that the flight recorders are processed in Russia, a source within the Russian investigation team told the Interfax news agency.

Russian President Vladimir Putin has declared Sunday a day of mourning while the authorities have set up an emergency center at the Saint Petersburg airport, where friends and relatives gathered, awaiting news of the victims.

German Chancellor Angela Merkel, US Secretary of State John Kerry, British Prime Minister David Cameron, as well as representatives of several other countries, have offered their condolences to Russia.

dj/jm (AFP, AP, dpa, Reuters, Interfax)