Health facilities across violence-ravaged Afghanistan are rapidly running out of supplies, and could also soon face a shortage of medical personnel, the World Health Organization warned Friday.

Twin suicide bombs ripped through crowds outside Kabul airport on Thursday, killing scores of Afghans as well as 13 US troops and adding to logistical difficulties faced by WHO to deliver medical equipment and medicine.

"We have only a few days of supplies left and are exploring all options to bring more medicines into the country," said Rick Brennan, the WHO emergencies director in the Eastern Mediterranean region.

Speaking to journalists in Geneva via videolink from Cairo, he acknowledged there were "multiple security and logistics constraints", adding that bringing supplies in through Kabul airport was no longer an option after the blasts.

The bombings, claimed by the Islamic State group, left scenes of carnage outside the airport where thousands of Afghans desperate to flee their Taliban-controlled country had massed.

A WHO partner, the Italian NGO Emergency, operates a hospital in Kabul and is "overwhelmed" following the blasts, Brennan said, adding "they've got great pressure on their supplies".

Brennan stressed the towering needs in Afghanistan even before Thursday's carnage and said that WHO had planned three airlifts of supplies into the country that had been cancelled following the Taliban takeover on August 15.

The UN, he said, was now looking at other options, including airlifting supplies through the Mazar-i-Sharif airport, with the first flights hopefully going in the next few days.

On a more positive note, Brennan said nearly all of the 2,200 health facilities the WHO was monitoring in the war-torn country remained open and functioning.

But he said there were also growing concerns about shortages of medical staff, many of whom are among those fleeing the country.

"We are hearing of healthcare workers leaving, health authorities leaving," he said, adding that the "enormous brain-drain ... is a big problem for all of us in every sector."

In addition, a number of women health workers were staying away from work, maybe out of fear, Brennan said. 

Many Afghans fear a repeat of the Taliban's brutal interpretation of Islamic law, as well as violent retribution for working with foreign militaries, Western missions or the previous US-backed government.

There are particular concerns for women, who were largely banned from education and employment and could only leave the house with a male chaperone during the group's 1996-2001 rule.