ITV News Correspondent Libby Wiener has spoken to a British passport holder stuck in Afghanistan who fears for his life
Boris Johnson has admitted to feeling "a great sense of regret" that not everybody eligible will be evacuated out of Afghanistan before the deadline.
"I obviously feel a great sense of regret that we aren’t able to get everybody out in this first phase," the prime minister said as the final evacuation flights left Kabul.
August 31 is the official deadline for the end of evacuation, but Mr Johnson said the UK operation is already in its "final hours".
Pressed on the scenes of chaos outside the airport, with many left desperate to flee the now Taliban-led country, the prime minister said to those eligible to come to the UK "We will shift heaven and earth to help them get out.
"We will do whatever we can in the second phase."
Boris Johnson: "I obviously feel a great sense of regret"
His comments come in the wake of the deadly bomb attack outside Kabul airport on Thursday, that killed at least 100, including two British nationals and the child of a third British national.
The PM said the Taliban understood the urgent need to relocate those qualified for safe passage to Western countries, as the final hours of the rescue efforts loom.
"As we come down to the final hours of the operation, there will also be people who haven't got through, people who might qualify,” Mr Johnson said.
He described the evacuations as "colossal" and unprecedented in modern times.
The airport gates have closed - what about those left behind? ITV News Political Correspondent Libby Wiener has more
"I think you need to look at the sheer scale and speed of what has been accomplished in the last few days," Mr Johnson added.
"Just since August 14, 13,000 people, plus 2,000 people before then. We’re talking about a very, very large operation. We’ve seen nothing like it in our lifetimes."
The Ministry of Defence confirmed on Friday that the UK's evacuation from Afghanistan has entered its final stages - no more people will be called forward to the airport for evacuation.
The latest news as the Kabul evacuation comes to an end:
The UK's evacuation from Kabul is now in its "final hours," PM feels "deep sense of regret" that not everybody will get out
The Ministry of Defence said processing facilities outside the airport have been closed
Two British nationals and the child of another British national among more than 100 killed in Thursday's twin bomb attacks
Why are evacuations coming to an end at Kabul airport?
Defence Secretary Ben Wallace insisted the withdrawal has nothing to do with the Kabul airport terror attack and the main UK evacuee processing site was closed "almost exactly on schedule."
US President Joe Biden committed to August 31 as the deadline for withdrawing US forces after inheriting a May 1 deadline from the deal signed by ex-president Donald Trump.
The UK has said the withdrawal of US troops meant British forces were forced to follow suit because America had been providing more than 95% of manpower and equipment on the ground.
It means that there would be a "few hundred" people who will be left behind.
How many people have been evacuated in Kabul and will more follow?
The Ministry of Defence has confirmed 13,708 people have been evacuated by the UK since August 13.
Afghan student Elham Barakzai was one of the lucky few to escape Kabul as she has a scholarship for a course in the UK.
Please raise our voices, don’t let us be silent.
Speaking from a hotel near Gatwick on behalf of those left behind, she told ITV News: "Please raise our voices, don’t let us be silent."
Her comments come as the processing facility inside the Baron Hotel in Kabul has now been closed.
The focus will be to evacuate people who have already been processed, to free up space to bring out military personnel and diplomats.
But Mr Wallace said: "The sad fact is not every single one will get out".
Mr Wallace tells ITV News the attacks have not put pressure on the decision to end evacuations soon
The Defence Secretary has said: "It is with deep regret that not everyone has been able to be evacuated in this process."He told ITV News: "About 36 hours ago, this was the time we had decided before the attacks happened.
"The US are leaving on the 31st of August but they had asked our military to leave before and therefore that knocks into the whole timetable."
Labour leader Sir Keir Starmer said the looming end of the evacuation from Kabul marks a "sad and dark day" and said the government has "serious questions to answer."
He said "with the withdrawal we face the heart-breaking reality that people have been left behind, including many to whom we owe so much".
Has the twin-bomb attack prompted evacuations to come to the final hours?
"It was nothing to do with the attacks," Mr Wallace told ITV News.
"The attacks had the effect of slowing down processing for a brief moment flights stopped and of course hours mean people."
He declined to give a timeline for the exit of British forces but acknowledged it would come before the Americans withdraw, with US President Joe Biden having set a departure date for Tuesday August 31.
Mr Wallace said: "The narrative is always going to be certain groups, such as IS, will want to stake a claim that they have driven out the US or the UK."
"We closed the Baron’s hotel almost exactly on schedule. The explosion was horrendous, but it didn’t hasten our departure," he added.
His comments come a day after President Joe Biden told a press briefing on Thursday that the attack was carried out by ISIS-K, an affiliate of the so-called Islamic State.
The US leader said his team had intelligence the group had been planning out "a complex set of attacks" on US forces and others - and said US commanders would strike back.
The president described the US troops who had lost their lives as "heroes" and said: "Our hearts ache for all those Afghan families who lost loved ones, including small children".
He vowed to make those responsible "pay".