BRUSSELS: NATO will hold an urgent meeting Friday on the deteriorating situation in Afghanistan after the US said it was sending troops to evacuate its nationals, diplomatic and official sources told AFP.

NATO Secretary General Jens Stoltenberg will lead discussions with envoys from the 30 allies in the meeting starting at 3:00pm (1300 GMT), with one source saying it would focus on evacuation planning from Afghanistan.

"It is about determining who does what, when, and how, and what support is given for this," the source said.

The Taliban has overrun a string of regional capitals in a lightning offensive since NATO troops largely pulled out of the country on the back of US President Joe Biden's decision to withdraw.

Leading NATO powers the US and Britain have ordered the deployment of thousands of troops to Afghanistan to evacuate their citizens.

Taliban near gates of Kabul as embassies prepare for evacuations

The moves came as the insurgents took control of Kandahar, the nation's second biggest city, leaving only the capital Kabul and pockets of other territory in government hands.

The government has now effectively lost control of most of the country, following an eight-day blitz into urban centres by the Taliban that has also stunned Kabul's Western backers.

Washington and London announced plans late Thursday to quickly pull out their embassy staff and other citizens from the capital.

A NATO official told AFP that the US had briefed its NATO allies ahead of the announcement by the State Department.

"NATO is monitoring the security situation very closely," the official said.

Taliban could isolate Kabul in 30 days, take over in 90: US intelligence

The official said the alliance was maintaining its own diplomatic presence in Afghanistan, but refused to give any details on the number of NATO staff still in the country for security reasons.