![The wreckage of a A321 Russian airliner in Wadi al-Zolomat in photo released by Russia's emergency ministry (1 November 2015)]()
Image copyrightAFP
Image caption The plane came down in a remote area of Egypt's Sinai peninsula ![Russian rescuer checking passports collected from the wreckage of crashed plane in photo released by Russia's Emergency Ministry (2 November 2015)]()
Image copyrightAFPImage caption Russian officials working at the crash site have collected passports from the wreckage
![David Cameron shakes hands with Egyptian President Abdel Fattah al-Sisi during their news conference at 10 Downing Street (5 November 2015)]()
Image copyrightGetty ImagesImage caption This is Mr Sisi's first official visit to the UK as Egyptian president
Sinai crash
Russia and Egypt have urged caution over suggestions from the UK and US that a Russian airliner that crashed in Sinai on Saturday may have been bombed.
The Russian foreign ministry said it was "shocking" that Britain had not shared the evidence.
Militants linked to Islamic State have claimed they brought the plane down. All 224 people on board, mostly Russian citizens, were killed.
The Metrojet Airbus 321, bound for St Petersburg, crashed in Egypt's Sinai desert just 23 minutes after take-off from Sharm el-Sheikh.
Image copyrightAFPImage caption Russian officials working at the crash site have collected passports from the wreckage UK Prime Minister David Cameron said intelligence obtained by its government suggested that a bomb was "more likely than not" to have brought down the airliner.
He and the Russian President Vladimir Putin spoke by phone on Thursday afternoon.
Media captionDavid Cameron: 'Huge sympathy' for Sharm holidaymakers
Egyptian President Abdel Fattah al-Sisi - in Downing St for talks on his first official visit to the UK - said that Egypt was completely ready to co-operate "with all our friends" over security measures at Sharm el-Sheikh airport.
Mr Cameron said that the UK and Egypt were "working intensively together".
His role was to "act in the right way" to keep British citizens safe and secure, he said.
Image copyrightGetty ImagesImage caption This is Mr Sisi's first official visit to the UK as Egyptian president "Intercepted communications" have led the US to conclude tentatively that the Russian plane may have been downed by a bomb planted by the IS affiliate Sinai Province, an official told AP.
Egypt's Civil Aviation Minister Hossam Kamal said investigators had "as yet no evidence" to confirm a bomb attack.
Egypt is leading the investigation, with the help of Russian and other foreign experts. They will examine the wreckage for traces of explosives, but would not reach their first conclusions for a few months, said Alexander Neradko, head of Russia's aviation agency.
In other developments:
- German airline Lufthansa says its subsidiaries Edelweiss and Eurowings are halting flights to Sharm el-Sheikh as a "precautionary" measure and will work with the German foreign ministry and holiday operators to arrange return flights for customers in the resort
- Belgian airline Jetairfly postponed its Thursday flight from Brussels to the Egyptian resort for 24 hours while it analysed the security situation
- The Netherlands is advising its citizens against travel to and from Sharm el-Sheikh airport
- Along with the UK, Ireland had announced the suspension of all flights to the resort on Wednesday
Lyse Doucet, BBC News, Cairo
The timing of Britain's statement on the air crash could not have been worse, just as President Sisi was arriving in London for his first official visit.
A senior official in his delegation told me this morning they were not told in advance. He said this would be one of the most important topics in today's meeting between the two leaders and would have an impact on other issues. We won't be as receptive, is how he put it.
Egyptian officials say they had responded to every British request for extra security at Sharm el-Sheik airport including additional troops in and around the airport.
This is a hugely embarrassing moment for the Egyptian authorities but, if it is proven that a bomb was on board the plane, they also face troubling questions about their ability to maintain security in the midst of significant threats.
Mr Cameron said it could be "some time" before thousands of UK tourists stranded in Sharm el-Sheikh were able to return.
"What we need to put in place is more security at that airport so it is safe to fly people home," he said.