Russian Plane Crash: Cameron Says 'More Likely Than Not' A Bomb, Kremlin 'Shocked' Intelligence Not Shared

David Cameron declared Thursday it was "more likely than not" that a bomb brought down a Metrojet flight packed with Russian tourists -- a scenario that Russian and Egyptian officials dismissed as premature speculation.

The prime minister said he had grounded all British flights to and from Sinai because of "intelligence and information" indicating that a bomb was the likely culprit in the crash Saturday that killed all 224 people onboard. The move stranded thousands of British tourists at the Red Sea resort of Sharm el-Sheikh.

David Cameron, right, holds a news conference with Egyptian President Abdel Fattah el-Sissi, Thursday, Nov. 5, 2015, at 10 Downing Street

Cameron said he had "every sympathy" with the Egyptians, who rely heavily on tourism, but added he had to "put the safety of British people first."

However, Russian Foreign Ministry spokeswoman Maria Zakharova said if Britain did have information about a bomb on the plane, it's "shocking" that hasn't been shared with Russia. “Frankly speaking, it is genuinely shocking to think that the British government has some kind of information that could cast light on what happened in the skies above Egypt. If such information exists, and judging by what the foreign secretary has said it does, no one has passed it to the Russian side,” she said.

The Islamic State group has claimed responsibility for bringing down the plane, a claim rejected by Russian and Egyptian officials as not credible. Egypt is, however, fighting an Islamic insurgency in the area where the plane crashed and Russia is supporting the Syrian government with airstrikes against IS targets.

Philip Hammond said the first of the 20,000 Britons stranded in Egypt may arrive back in the UK on Friday

"We don't know for certain that it was a terrorist bomb... (but it's a) strong possibility," Cameron said at 10 Downing Street shortly before a previously scheduled meeting with Egypt's president. "There's still an investigation taking place in Egypt. We need to see the results of that investigation."

On Thursday afternoon, Cameron and Russian President Vladimir Putin spoke about the crash in a phone call. The Kremlin said Putin told the British leader it's necessary to rely on data yielded by the official crash probe while assessing the reason for the crash. The two men discussed the joint fight against terror.

A British team was in Egypt working with officials to tighten security at the Sharm el-Sheikh airport so the British flights could resume. Cameron said "we want to start as soon as possible" to bring tourists home, and empty planes would be flying out from Britain to do that, but the process would take some time.

After meeting with Cameron, Egyptian President Abdel-Fattah el-Sissi said British officials had sent a security team to check Sharm el-Sheikh airport 10 months ago and were satisfied with the results. "They checked the security actions, they were happy with that," he told a news conference, speaking through an interpreter. Egypt stands "completely ready to cooperate with all of our friends" to ensure the safety of foreign tourists.

Egyptian Military experts examine a piece of an engine at the wreckage of a passenger jet bound for St. Petersburg in Russia that crashed in Hassana, Egypt, on Sunday, Nov. 1, 2015

Putin's spokesman, Dmitry Peskov, insisted that investigators were working on all possible theories as to why the Airbus A321-200 crashed Saturday in Egypt's Sinai Peninsula just 23 minutes after taking off from Sharm el-Sheikh. He said naming just one possibility was mere speculation. "One cannot rule out a single theory, but at this point there are no reasons to voice just one theory as reliable -- only investigators can do that," Peskov told reporters in Moscow.

In Sharm el-Sheikh, British tourists backed the flight ban but also spoke of their fondness for the resort. "We understand why the government have done it, but I am really worried for the Egyptian people because -- particularly in the Red Sea resorts -- they are so dependent on tourism," said Paul Modley, a 49-year-old Londoner who has travelled to the town seven times in the last nine years.

SEE ALSO:

• ISIS Claim It Brought Down Russian Plane Rubbished

• Investigation Into Crashed Airliner Suggest It 'Broke Up In Mid-Air'
• More Than 200 People Confirmed Dead In Egypt Plane Crash