The UN has urged Afghanistan’s neighbours to keep their borders open as the number of civilians fleeing the Taliban onslaught swells.
Many of those internally displaced have been arriving in Kabul, seeing the capital as their last safe refuge.
Food shortages are “dire”, the World Food Programme (WFP) said. It warned of a humanitarian catastrophe.
On Friday, the Taliban seized the country’s second largest city Kandahar, the latest provincial capital to fall.
The southern city of 600,000 people was once the Taliban’s stronghold, and is strategically important as a trade hub.
The insurgents also took the nearby city of Lashkar Gah and now control about a third of Afghanistan’s provincial capitals.
Many of those seeking safety in Kabul are sleeping on the streets. About 72,000 children are among those fleeing to the capital in recent days, according to Save the Children.
“We have no money to buy bread, or get some medicine for my child,” a 35-year-old street vendor who fled northern Kunduz province after the Taliban set fire to his home
Makeshift camps have been established on scrubland on the outskirts of the capital, while many others have reportedly been sleeping in abandoned warehouses.
More than 1,000 civilians have been killed in Afghanistan in the past month, according to the UN.
The insurgent advance comes as US and other foreign troops withdraw after 20 years of military operations.
The US is to send nearly 3,000 troops to Kabul airport to evacuate a “significant” number of embassy staff on special flights. The UK is deploying 600 troops to support British nationals leaving the country. Staff at the British embassy have been reduced to a core team.