The British government has ordered the suspension of all flights to and from Egypt's Sinai Peninsula over concerns a Russian plane that crashed there at the weekend was downed by an "explosive device". The move comes after the Egyptian branch of Islamic State (Isis) released an audio statement reiterating its claim to have brought down flight 7K9268 from the Red Sea resort of Sharm el-Sheikh to St Petersburg, killing all 224 people on board.

A spokesperson for Prime Minister David Cameron said it was a precautionary measure pending the ongoing investigation into the incident. "While the investigation is still ongoing we cannot say categorically why the Russian jet crashed," the spokesperson said. "But as more information has come to light, we have become concerned that the plane may well have been brought down by an explosive device." The government said extra consular staff has been deployed to help Britons in the renowned diving resort.

Earlier on 4 November, Abu Osama al-Masri, the spokesman of IS's Egyptian offshoot Sinai Province, claimed in an audio message that the Kogalymavia Airlines flight was brought down. "We are the ones who brought it down," he said, adding the method will be revealed "in the time of our choosing".

The Airbus A321 broke up in mid-air 23 minutes after taking off from Sharm el-Sheikh airport on 31 October. It crashed in the Hassana area of the restive Sinai peninsula, where Islamist militants are leading an insurgency against the government.

Security analysts, as well as Russian and Egyptian officials, have cast doubt over IS's claims of responsibility. It seems unlikely that with the weapons systems at its disposal the Sinai Province militants would be able to down a commercial jet cruising at more than 30,000ft. Russian Transport Minister Maxim Sokolov called the claims a "fabrication".

Aviation experts have speculated whether technical failure or an explosion could have brought the plane down, with the first option being initially the most credited. Earlier this week, officials with Kogalymavia, also known as Metrojet, claimed a "mechanical impact on the plane" had caused it to go down.

Russian media reports claimed forensics analysis revealed some passengers suffered blast injuries and burns. Several airlines, including Emirates, Lufthansa and Air France-KLM, have nevertheless said they will not fly over the area until reasons for the crash are clear.

The jet was cruising at about 31,000ft, when in one minute, it lost 5,000ft and of 300kph (186mph) in speed, according Metrojet's deputy general director, Alexander Smirnov. The crew "totally lost control" and was not able to radio aviation authorities.

British government statement in full

A Number 10 spokesperson said:

"We want to update you on our response to the plane crash in Sinai this weekend.

Since then, we have been following the investigation closely to make sure that we take any steps necessary to ensure the safety of British citizens on flights from Sharm. That will always be our priority.

The Prime Minister called President Sisi yesterday evening to discuss what measures the Egyptians are taking to ensure the tightest possible security arrangements at Sharm el-Sheikh airport.

While the investigation is still ongoing we cannot say categorically why the Russian jet crashed. But as more information has come to light we have become concerned that the plane may well have been brought down by an explosive device.

In light of this and as a precautionary measure we have decided that flights due to leave Sharm for the UK this evening will be delayed. That will allow time for a team of UK aviation experts, currently travelling to Sharm, to make an assessment of the security arrangements in place at the airport and to identify whether any further action is required. We expect this assessment to be completed tonight.

In terms of flights from the UK to Sharm, there are no more departures today.

We would underline that this is a precautionary step and we are working closely with the airlines on this approach. The Prime Minister will chair a COBR at 6:45pm to review the situation and we will provide an update after that meeting.

We recognise that this information may cause concern for those in Sharm and indeed for those planning to travel to Sharm in the coming days. We have deployed extra consular staff to Sharm who will be on hand at the airport, working with the airlines, to assist British holidaymakers there. For others, either in resorts at Sharm or planning a holiday to Sharm in the coming days, our advice is to contact your airline or tour operator.

At this stage we are not changing the level of our travel advice."