A plane carrying the remains of 144 people killed when a Russian airliner crashed in Egypt has landed in Saint Petersburg, hours after investigators probing the doomed flight said it had broken up in the air.
The emergency Russian plane, the first to bring back the bodies of those who died when the A-321 plummeted from the sky above the restive Sinai Peninsula, arrived in the Pulkovo airport of Russia's second-largest city.
Investigators from several countries have joined an Egypt-led probe to determine what brought down Russian airline Kogalymavia's flight 9268 on Saturday (local time), killing all 224 people on board, en route from Sharm el-Sheikh to Saint Petersburg.
They have recovered the "black box" flight recorders of the Airbus, and the head of an Irish mission that will join the Egypt-led probe into the disaster said the results from the recorders should be ready in a few days.
The head of the Russian air transport agency Alexander Neradko on Sunday said it appeared the aircraft disintegrated while flying at high altitude, echoing similar comments from other top aviation officials.
"All signs prove that the structure of the plane disintegrated in the air at a high altitude," he told Russian state television.
The bodies of those sent back to Saint Petersburg were due to be taken in a motorcade to a crematorium for identification, which will begin later on Monday, according to Russia's emergency ministry.
Russian officials confirmed that 144 bodies were on board the plane which landed at Saint Petersburg.
Egypt had earlier said the remains of 162 people would be flown back, out of 214 Russian passengers said to have been on the flight, along with three Ukrainians and seven crew.
Family members have been providing DNA samples at a crisis centre set up close to the Russian airport, now the site of an impromptu memorial where people have brought flowers and cuddly toys to commemorate the victims, many of them children.
Flags flew at half-mast in Russia on Sunday on a national day of mourning for the victims, and thousands gathered in Saint Petersburg's Palace Square to observe a minute's silence and release doves and balloons into the darkening sky.
Officers involved in the search efforts said rescue crews had recovered 168 bodies so far, including one of a girl found eight kilometres from the main wreckage.
Experts have dismissed claims from an IS-affiliated insurgency group in the Sinai that it brought down the aircraft in revenge for Russian air strikes against the jihadist group in Syria.
They argue the militants have neither the technology nor the expertise to down a plane flying at 9000 metres, although Germany's Lufthansa, Emirates and Air France have all halted flights over Sinai until the reasons for the crash were known.
Experts say human or technical error more likely caused the crash.