A VICTIM LAID TO REST....

The funeral in Russia on Thursday of Aleksei Alekseev, who died in the crash in Egypt. Credit Vasily Maximov/Agence France-Presse — Getty Images

“My role is to act in the right way to keep British citizens safe and secure,” Mr. Cameron said. He did not cite what specific intelligence he had suggesting that the explosion that destroyed the Russian plane about a half-hour after it took off from Sharm el Sheikh was deliberate.

Mr. Sisi, who has counseled against jumping to premature conclusions, did not criticize Mr. Cameron’s decision to temporarily suspend flights between Britain and Sharm el Sheikh, but Egyptian officials in Cairo did just that.

Hossam Kamal, the Egyptian minister of civil aviation, said that the suggestion of a bomb was not based on facts — and that there was as yet no evidence for that theory. The Ministry of Foreign Affairs said the British government had made the decision to halt flights unilaterally.

In a telephone conversation on Thursday with Mr. Cameron, President Vladimir V. Putin of Russia also took exception to his comments, saying that any “assessment of the causes of the crash should be based on the data” from the investigation, the Kremlin said in a statement.

While there has been much speculation about what brought down the jet, the cause largely remains a mystery. American military officials said this week that satellite surveillance had detected a flash of light as the plane was ripped apart, suggesting that it had been blown up by a bomb, an explosion caused by a mechanical failure or the ignition of fuel.

Mr. Sisi, standing next to Mr. Cameron, acknowledged that Britain had previously raised safety concerns. “Ten months ago, we were asked by our British friends to send teams to Sharm el Sheikh airport to make sure that all our security procedures there were good enough, and to provide adequate safety and security for our passengers,” he said, adding that the Egyptian authorities were ready to address any outstanding concerns.

The prime minister’s office announced later Thursday that British and Egyptian officials had “agreed on a package of additional security measures that is being put in place rapidly,” and that flights to Britain from Sharm el Sheikh would resume Friday. Two British airlines, Monarch and EasyJet, said they were ready to run flights to bring stranded tourists back to Britain from the Red Sea resort, where there are an estimated 20,000 British citizens.

Flights to Sharm el Sheikh from Britain remained suspended.

Two subsidiaries of the German airline Lufthansa, the Düsseldorf-based Eurowings and Edelweiss Air, which operates out of Zurich, suspended their Sharm el Sheikh flights on Thursday. Lufthansa said the group was working out a plan to help passengers return home.

Aleksandr Neradko, head of the Federal Air Transport Agency in Russia, said investigators in Egypt looking into the crash would be examining the wreckage of the airplane, including the hand baggage and victims’ bodies to see if there were traces of explosive substances.

Also on Thursday, the first two funerals were held for victims of the crash. The funeral for Nina Lushchenko, 60, who ran a school canteen, was a traditional Orthodox service at a 16th-century church in Veliky Novgorod, about 125 miles south of St. Petersburg.

The funeral for another victim, Aleksei Alekseev, 31, took place in St. Petersburg.