LONDON — Prime Minister David Cameron of Britain said on Thursday that “more likely than not a terrorist bomb” had brought down the Russian chartered jet that broke apart over the Sinai Peninsula last Saturday, despite criticisms from officials in Egypt and Russia that his assessment was premature.
Mr. Cameron defended his government’s decision on Wednesday to suspend flights between Britain and the Egyptian resort city of Sharm el Sheikh. In a joint appearance at No. 10 Downing Street with the Egyptian president, Abdel Fattah el-Sisi, Mr. Cameron said, “My role is to act in the right way to keep British citizens safe and secure.” He did not cite any specific intelligence that suggests a bomb had caused the crash, which killed all 224 people on board.
Mr. Sisi declined to criticize Mr. Cameron but in Cairo, Egyptian officials did just that. Hossam Kamal, the Egyptian minister of civil aviation, said 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, without consulting Egypt.
Earlier on Thursday, in a phone call with Mr. Cameron, Russia’s president, Vladimir V. Putin, 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 it had been blown up by a bomb, a mechanical failure or an accidental explosion of fuel. But counterterrorism officials have cautioned strongly against jumping to premature conclusions.
The British government estimated that it could take a week to fly the roughly 20,000 British citizens on the Sinai Peninsula back home. Two British airlines, Monarch and EasyJet, said that they would run flights to bring stranded tourists back to Britain, but that they had halted all outbound flights to the Red Sea resort.
The British government has gone well beyond that of any other country — including the United States — in its public assessment of the crash.
An insurgency affiliated with the Islamic State has been battling the Egyptian military on the peninsula, which is closed to visitors with the exception of Sharm el Sheikh.
Mr. Cameron acknowledged that “we need to see the results” of the Egyptian investigation but he told the BBC: “The decisions that I’m taking are about putting the safety of British people first.”
Mr. Sisi, standing next to Mr. Cameron in London, 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.
Russian officials said on Thursday that no theory of what had caused the crash could be discounted. “Naturally, all information is being accumulated and delivered to the chief of state,” the news agency Interfax quoted the Kremlin’s press secretary, Dmitri S. Peskov, as saying. “Not a single theory can be ruled out, but there are no grounds to declare at least one of these theories more or less reliable as of yet. This can be done only by investigators.”
Asked whether the theory that terrorism felled the plane might affect Russian policy in Syria, Mr. Peskov said, “Hypothetical presumptions of this kind are totally inappropriate.”