The World Food Programme says 14 million people in Afghanistan could starve without urgent aid.
A WFP exec said the COVID-19 pandemic, a drought, and the Taliban takeover caused a "perfect storm."
Others have raised alarm; UNICEF says 10 million Afghan children need aid to survive this year.
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United Nations agencies have warned that millions in Afghanistan could starve without foreign aid as a combination of drought, the COVID-19 pandemic, and the Taliban's takeover plunges the country into a food shortage.
"The number of people marching to starvation has spiked to now 14 million," David Beasley, the World Food Programme's executive director, told Reuters on Tuesday, urging political leaders to act quickly and calling the series of events a "perfect storm."
WFP is hoping to raise $200 million in the next few weeks to feed Afghans through the winter, it reported. The organization is concerned that without additional funding the country may run out of wheat flour by October.
The World Health Organization on Monday said the flow of emergency supplies including food into Afghanistan ground to a halt when Hamid Karzai International Airport in the Afghan capital of Kabul closed to commercial flights to facilitate evacuations. It said over 18 million people in the country of roughly 38 million were in need of aid.
"While the main focus over the past days has been major air operations for the evacuation of internationals and vulnerable Afghans, the massive humanitarian needs facing the majority of the population should not - and cannot - be neglected," WHO wrote in its statement.
Dr. Richard Brennan, WHO's emergency director for the Eastern Mediterranean, requested that empty planes traveling to Afghanistan to evacuate people first divert to the organization's warehouse in Dubai, United Arab Emirates, to pick up supplies, per an email statement to The Guardian.
On Monday, UNICEF released a statement saying that 10 million children in Afghanistan required humanitarian assistance to survive. About 1 million are projected to suffer from malnutrition this year and could die without treatment.
Malnutrition among children has been a widespread health issue in Afghanistan for years. It is detrimental to children's intellect, overall health, and future productivity. Afghanistan has a 41% rate of stunting - one of the highest in the world - among children under 5 years old, a sign they are regularly underfed in critical periods of their growth, per UNICEF.
"Millions will continue to need essential services, including health, lifesaving vaccination drives against polio and measles, nutrition, protection, shelter, water, and sanitation," its Monday statement said.