US President Joe Biden has pledged retribution for the killings of Americans, announcing from the White House he will "hunt" down those responsible. 

Ardern described the attack on the airport as "despicable", and thanked the US, Australia and the United Arab Emirates for assisting New Zealand's mission. 

"In Afghanistan right now it has been publicly reported that a number of prisons have been essentially opened up and those previously detained have been released, and obviously those will be across both Taliban, and as I understand, ISIS," Ardern said. 

"You can see that the environment there is dangerous and volatile... This is a demonstration of a terrorist attack and a demonstration of what is a very complex situation on the ground."

What happens next?

So far, 276 New Zealanders and permanent residents, their families, and other visa holders have been evacuated from Kabul destined for New Zealand. 

Of the 276, 228 have already departed the United Arab Emirates for New Zealand. These numbers are likely to change as processing of those onboard partner flights continues. 

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An additional group of 100 people, including Kiwis and Australians, were taken on the final flight on Thursday night out of Kabul via the Defence Force's C-130 Hercules. There were eight hours between the flight's lift off and the explosions. 

The exact number of those destined for New Zealand that were on board that flight will be available once current processing is complete.

"Of those we know were registered on Safe Travel, on Friday 13 we had 11 registered on Safe Travel... as of yesterday, we had 520 registered on Safe Travel," Ardern told reporters on Friday. 

"I cannot tell you how many of those who are registered were amongst those we have already evacuated. We do know that we had over 270 and there will be an additional up to 100, some of those will be Australian, that we are still yet to process. 

"We are just unfortunately not clear on the numbers. 

"Firstly, not everyone may have registered on Safe Travel. Secondly, of those who hold visas from Afghanistan, we don't know how many of them were in Afghanistan at the time. And finally, we don't know how many of those registered we did manage to get out." 

But Ardern is certain not everyone got out that New Zealand wanted to, and with allies quickly withdrawing due to the dangerous situation on the ground, it will be difficult to get them out. 

Though she is not giving up on them. 

"Some consolidation will be required, but I can say, we know with absolute certainty we did not get everyone out," Ardern said. 

"I was speaking with [German] Chancellor [Angela] Merkel last night in quite some detail about the situation in Afghanistan and there remain a number of international partners and others who will be continuing to seek ways to bring out those who they were unable to evacuate. 

"New Zealand is not alone in this. 

"As a Cabinet, we will consider what those options are, but we'll be looking to our international partners for those conversations, because they will be in the same position as us. My understanding is that most of our international partners are now withdrawing."

Cabinet will also consider allowing more Afghan refugees into New Zealand. 

NZDF Chief Kevin Short said eight other nations also finished their flights into Kabul and it's believed another four will withdraw. That will leave the US and the UK continuing operations. 

The US has promised to pull out at the end of the month, as per a deal struck with the Taliban under former President Donald Trump, in exchange for safe passage of American troops out of the country. But now the situation has changed, Biden has indicated he may keep troops in Afghanistan. 

The President said he told the US military he would grant additional force if they needed it, saying: "Whatever they need, if they need additional force, I will grant it."

How did the Defence Force get people out?

Over the course of the mission, the NZDF undertook three flights out of Kabul and successfully brought out hundreds of evacuees who were destined for both New Zealand and Australia.

Short said the NZDF C-130 Hercules aircraft will remain in the United Arab Emirates until September 6 to allow time to evacuate the remaining Kiwis and eligible Afghans. 

He provided extraordinary insights into how NZDF officials were able to identify eligible Afghans and assist them in getting to the airport in Kabul. 

"A foreign affairs representative working in the Tehran embassy was talking to individuals on the ground - this is Afghan nationals - and identifying them by having them take photos of themselves and their visa and whatever information they could provide. 

"That was then passed to the men and women on the ground. We had 19 on the ground in Kabul. They could then go out and find them within the crowd with the identification. 

"This process was going on continually. 

"Then they were asking them to go via safe routes to get past a Taliban outer circle, through the crowds, and then within the crowds there are areas where our people were picking them out. 

"We had directions on how to get into the airport safely, as in crossing canals, going under fences, particular gates, through to identifying them because of pictures that were taken just minutes before that helped our people identify them, and then taken into the safe haven."