People who want to flee the country continue to wait around Hamid Karzai International Airport in Kabul, Afghanistan on August 25, 2021.

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LONDON – UK officials warn of a “very credible” threat of an attack on Kabul airport by Islamic State militants.

It comes as massive evacuation efforts enter the final stages as countries seek to evacuate people from Taliban-controlled Afghanistan before President Joe Biden’s August 31 deadline.

Some European countries have already started to suspend flights from Hamid Karzai International Airport.

The US and other western countries involved in the evacuation have urged people to stay away from the airport amid growing concerns about possible terrorist activities.

British Army Secretary James Heappey told Sky News on Thursday that an “immediate fatal attack” could take place at Kabul airport.

“The intelligence services have become increasingly safer as the week goes on to prevent the highly credible impending fatal attack on the airport or the handling centers used by Western forces,” Heappey told Sky News.

The British Foreign, Commonwealth and Development Office has meanwhile issued new guidelines to warn of “a persistent and high threat from terrorist attacks”. It urged people not to travel to the airport and move to a safe place to wait for further advice.

Passengers evacuated from Afghanistan leave on Aug.

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Late on Wednesday, the U.S. embassy in Kabul urged U.S. citizens in Afghanistan to avoid traveling to the capital’s airport, citing an unspecified security threat at the gates.

“Due to security threats outside the gates of Kabul Airport, we advise US citizens not to travel to the airport at this time and avoid airport gates unless they are instructed to do so by a US government representative,” said it in the security warning.

“US citizens who are now at Abbey Gate, East Gate or North Gate should leave immediately,” she added.

The US embassy in Kabul advised Americans to be aware of their surroundings at all times, to follow instructions from local authorities, draw up an emergency plan, and monitor the local media and the State Department for developments.

Evacuations are entering the final phase

The US government has not disclosed the total number of Americans and Afghan nationals it plans to evacuate before troops withdraw by the end of the month.

NATO allies and members of the president’s own party pushed for an extension of the exit period and expressed doubts that the coalition can evacuate all Afghans who are entitled to leave in such a short time.

However, Biden reaffirmed Tuesday to leaders of the G-7, NATO, the United Nations and the European Union that the United States will withdraw its military from Afghanistan by the end of the month.

Denmark said its last flight from the Afghan capital was on Thursday, with Defense Minister Trine Bramsen reportedly warning: “It is no longer safe to fly into or out of Kabul.”

The Dutch government also expects to conduct its last evacuation flight on Thursday due to the deteriorating security situation, reported Reuters. She described the decision as a “painful moment” as people who come to the country for an evacuation are now being left behind.

French Prime Minister Jean Castex told French radio RTL on Thursday that the country would no longer be able to evacuate people from Friday evening as a result of the American withdrawal.

– CNBC’s Amanda Macias contributed to this report.