Russian tourists from Sharm el-Sheikh arrive at the Domodedovo International airport, outside Moscow, on Sunday.

AFP/Sharm el-Sheikh

Moscow and London ramped up efforts on Sunday to bring home thousands of tourists stranded in Egypt's Sharm el-Sheikh resort following the crash of a Russian airliner in the Sinai Peninsula.

Britain and the US, as well as international investigators, suspect a bomb exploded on board the Russian Airbus after it took off from the Red Sea resort last Saturday en route to Saint Petersburg, killing all 224 people on board.

The Islamic State group's branch in the Sinai has claimed responsibility, but Egyptian officials insist there is no evidence yet of an attack on the plane.

Security fears nonetheless saw Russia stop all flights to Egypt and Britain halt air travel to Sharm el-Sheikh, while several other countries have warned their nationals not to fly to the resort.

Tens of thousands of people have been left stranded for days by the clampdown, which Egypt fears could deal a heavy blow to its vital tourism industry, already battered by years of unrest.

Russia said it would send 44 planes to bring its nationals home, with some 80,000 Russians estimated to be in Egypt, mainly in Sharm el-Sheikh and another Red Sea resort, Hurghada.

Russian Deputy Prime Minister Arkady Dvorkovich told reporters at a Moscow airport on Sunday that some 11,000 Russian tourists had been repatriated in the previous 24 hours.

"Today is the busiest day in this sense," he said, adding that more people were set to return home later on Sunday.

The Kremlin has insisted the decision to suspend flights does not mean Moscow believes the crash was caused by a deliberate attack.

Increasingly frustrated  

But Dvorkovich said Russia was sending experts to inspect Egypt's airports to see if security needed to be beefed up there.

Around 3,300 of the Britons in Sharm el-Sheikh have been brought home on jets laid on by airlines in conjunction with the government, and a further 1,700 are expected home on Sunday, Foreign Secretary Philip Hammond said.

Hammond said the British government would push for higher security at foreign airports in risky areas, even if it means extra delays for passengers.

"What we've got to do is ensure that... airport security reflects local conditions," he told the BBC.

"Where there's a local higher threat, that will mean higher levels of security are required and that may mean additional costs and may mean additional delays at airports."

Forced to extend their stays, impatient British tourists were growing increasingly frustrated.

"The hotel and its staff are great, but the airline has not called us, nor telephoned or emailed," said Rob Ashford, 27, who had been due to fly home to Manchester on Friday.

"We have been told not to step out of the hotel for security reasons," he said.

Flight numbers have been limited because both Russia and Britain have banned tourists from bringing their check-in luggage, which will be flown home separately.

That restriction has prompted Egypt to limit the number of daily repatriation flights because it says there is only so much baggage its airports can accommodate.

On Saturday the head of Egypt's investigative committee said the cause of the crash was still not clear.

"Initial observations... do not allow for identifying the origin of the in-flight break-up" of the aircraft 23 minutes and 14 seconds after it departed, Ayman el-Mokkadem said.

Bells toll for victims  

Sources close to the probe have told AFP that experts involved in the investigation, with the exception of the Egyptians, "strongly favour" the theory of a bomb on board.

One source said there was only an "infinitely small" chance that a technical incident was behind the "sudden explosive decompression" on the plane suggested by an analysis of its black box flight data and voice recorders.

IS said it downed the plane in retaliation for Russian air strikes in Syria, but has not said how.

If it was behind the attack, it would be the first time the jihadists, who control large areas of Syria and Iraq, have hit a passenger plane.

The IS affiliate in Egypt is waging a bloody insurgency in north Sinai that has killed hundreds of policemen and soldiers.

In Saint Petersburg, mourners remembered the victims in a ceremony that saw the bells of the iconic St. Isaac's Cathedral tolling 224 times in memory of each person killed.

One of the mourners, Alla Mikhailova, said she could not stop thinking about the crash, Russia's deadliest aviation tragedy.

"A week has passed but I still cannot come to my senses," the 38-year-old told AFP. "I believe this, this wound will remain with us forever."