NATO Secretary General Jens Stoltenberg has said the alliance was surprised by the speed of the Taliban victory in Afghanistan but blamed Afghan leaders for the "tragedy".
"Ultimately, the Afghan political leadership failed to stand up to the Taliban and to achieve the peaceful solution that Afghans desperately wanted," he said.
"This failure of the Afghan leadership led to the tragedy we are witnessing today."
Mr Stoltenberg told reporters that the alliance was now working to ensure the safety of NATO's remaining civilian personnel and Afghan employees in Afghanistan.
Taliban rebels overran the Afghan capital at the weekend after the Western-backed government and resistance from its US and NATO-trained forces collapsed.
Staff from Western embassies have relocated to the city's airport, which is under the protection of a rear-guard of US troops deployed to cover the allied retreat.
"NATO has been working around the clock to maintain operations at the Kabul International Airport," Mr Stoltenberg said, after a meeting of senior NATO diplomats from alliance members.
"Around 800 NATO civilian personnel have remained to provide key functions under very challenging circumstances, including air traffic control, fuel and communications."
"Let me also thank the military forces of NATO allies - in particular Turkey, the United States and United Kingdom - for a vital role in securing the airport.
Mr Stoltenberg said NATO's senior civilian representative in Afghanistan, Ambassador Stefano Pontecorvo, would remain at the airport "to coordinate and facilitate the evacuation" of NATO staff and Afghan employees.
"The Taliban must respect and facilitate the safe departure all those who wish to leave the airport and, as well, roads and border crossings must be open," he said.
"All Afghan men, women and children deserve to live in safety and dignity."
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Meanwhile, Minister for Foreign Affairs Simon Coveney joined his European Union counterparts for emergency talks via videolink today on the unfolding developments in Afghanistan.
Speaking after the videolink talks, EU foreign policy chief Josep Borrell said that while the fight against Al Qaeda in Afghanistan succeeded, the process of nation-building failed despite the enormous amount of resources directed to the country.
"And the main conclusions of this meeting has been that the first objective, the priority, is to ensure the evacuation in the best conditions of security of the European nationals still present in the country, and also of the Afghan citizens who worked with us for more than 20 years, if they want to leave the country," he said.
The EU will only cooperate with the Afghan government following the Taliban's return to power if it respects fundamental rights, including women, and prevents the use of Afghanistan's territory by terrorists, Mr Borrell said.
"Cooperation with any future Afghan government will be conditioned on a peaceful and inclusive settlement and respect for the fundamental rights of all Afghans, including women, youth and persons belonging to minorities, as well as respect for Afghanistan's international obligations, commitment to the fight against corruption and preventing the use of Afghanistan’s territory by terrorist organisations," he said in a statement.
Mr Coveney said: "In the discussion with my European colleagues I expressed Ireland's grave concern at the situation for women and girls in Afghanistan, as we also made clear at the UN Security Council yesterday.
"The EU has been clear on the conditionality we will attach to support to any future Afghan government, particularly the need for a peaceful and inclusive settlement and respect for fundamental rights of all Afghans.
"EU member states are coordinating intensively on the evacuation of EU citizens, as well as on Afghan staff working with EU embassies and organisations."
Mr Coveney said that work is ongoing to finalise the processing of places for up to 150 Afghan nationals and their families under the Refugee Protection Programme.
He said that Ireland will organise a meeting this week of the UN Security Council informal expert group on Women, Peace and Security, specifically focused on Afghanistan.
Member states and the EU executive in Brussels are attempting to pull their foreign and Afghan staff out of the capital, Kabul.
EU officials have been pleading with the bloc's 27 capitals to give visas to Afghan workers at the EU mission in Kabul and their families, estimated to number around 500, European diplomats said.
The European Commission has no power to issue visas on its own behalf.
Diplomats said member states now appeared to be pledging enough visas to cover the EU's staff, including local Afghan hires, but the question was how to get them out of the country given chaos at the airport.
An Irish Minister of State said he expects the allocation of visas for people from Afghanistan to increase over the coming days and weeks.
The Government has announced it will allocate 150 humanitarian visas for Afghans, who want to leave the country, in addition to 45 visas already approved under the Irish Refugee Protection Programme in recent days.
Individual European countries were also scrambling to fly out their nationals and Afghan employees as crowds mobbed the airport in Kabul frantic to board departing planes.
