The head of Britain's domestic intelligence service said that Afghanistan is becoming a hotbed for terrorism.
A British man was one of two suspected ISIS recruits caught while trying to enter Afghanistan this month.
Ken McCallum, the director general of MI5, said the service has evidence of terrorist groups regrouping in Afghanistan and recruits are travelling to join them.
In September Mr McCallum said that the Taliban takeover of Afghanistan would give a "morale boost" to extremists in the UK and that terrorist groups would begin "reconstituting themselves within Afghanistan and projecting the threat back at the West including the UK".
"We have seen versions of both of those risks beginning to materialise," he told the Daily Mail in an interview.
"Clearly we have seen some people interested in travelling to Afghanistan in pursuit of some of those goals.
"We have seen the beginnings of some travel attempts, and so with our partners we remain very vigilant."
After the Taliban regained control of Afghanistan in August there were fears that the country would again become a safe haven for terrorist groups despite Taliban leaders vowing not to shelter such people.
ISIS’s affiliate in Afghanistan, known as ISIS-K, is the most extreme and violent militant group in the landlocked country.
In August the group claimed responsibility for a suicide bombing outside Kabul Airport that killed 170 Afghan civilians and 13 US military personnel who had been involved in evacuation efforts.
In February, the Taliban arrested two men, one with a British passport, at a border crossing in northern Afghanistan on suspicion of being ISIS recruits.
The pair had tried to enter through the town of Hairatan, which straddles Uzbekistan and Afghanistan.
They were carrying more than £10,000 in cash, military fatigues and night-vision goggles.
Mr McCallum said he believed two years of coronavirus pandemic have helped to inspire potential terrorists to use biological weapons.
"It will have occurred to many people that biological or viral agents can be tools of significant game-changing events," he said.
"It does not automatically follow that anyone having that thought has the wherewithal to do something intelligent about it," he said.
"But this has always been one of the risks that we are mindful of and seek to manage."