The Taliban's newly appointed envoy to the United Nations urged quick world recognition of Afghanistan's new rulers even as the World Health Organisation raised the alarm of an impending health care disaster in the war-wracked country.

The humanitarian crisis is one of the many challenges the Taliban face since their takeover of Afghanistan last month, including renewed threats from the militant Islamic State group, which recently stepped up its attacks, targeting members of the Taliban in its stronghold in the country's east.

In an emergency measure, the UN aid coordinator Martin Griffiths released 45 million US dollars in life-saving support for Afghanistan from the world body's emergency fund.

The World Health Organisation said Afghanistan's health system is on the brink of collapse and that urgent action is needed.

The statement followed a recent visit to Kabul by a WHO team led by the agency's director-general, Tedros Adhanom Ghebreyesus, who also met with Taliban leaders and others.

"The country faces an imminent humanitarian catastrophe," WHO said, adding that thousands of health facilities are without funding for medical supplies and salaries for health staff.

"Many of these facilities have now reduced operations or shut down, forcing health providers to make hard decisions on who to save and who to let die," WHO said and also emphasised "the need for women to maintain access to education, health care, and to the health workforce".

Mr Griffiths warned that "allowing Afghanistan's health-care delivery system to fall apart would be disastrous".

People across Afghanistan, he added, "would be denied access to primary health care such as emergency Caesarian sections and trauma care".

Earlier, the Taliban had written to the United Nations announcing that Suhail Shaheen, a former peace negotiator and spokesman for the Taliban political office, is their new UN representative.

They requested that Mr Shaheen be allowed to address the UN General Assembly under way in New York.

"We have all the requirements needed for recognition of a government.

"So we hope the UN, as a neutral world body, recognise the current government of Afghanistan," Mr Shaheen said.

Afghanistan is listed as the final speaker of the ministerial meeting on Monday, and if no world recognition of the Taliban comes by then, Afghan ambassador Ghulam Isaczai will give the address.

Mr Isaczai is currently recognised as his country's UN ambassador but the Taliban, who overran most of Afghanistan last month as the US and Nato forces were in the final stages of their chaotic withdrawal from the country, argue that they are now in charge and have the right to appoint ambassadors.

Since they swept to power and Afghan President Ashraf Ghani fled the country, the Taliban have appointed an all-male cabinet made up mostly of hardliners from when they previously ruled Afghanistan in the late 1990s, including several people on the UN sanctions list.

Among those on the so called UN "black list" is Amir Khan Mutaqqi, the Taliban foreign minister and the author of the letter to the UN, requesting Mr Shaheen address the General Assembly.

The decision rests with a UN committee that generally meets in November and will issue a ruling "in due course", the General Assembly's spokeswoman Monica Grayley said.

Meanwhile, attackers hit vehicles with Taliban fighters in eastern Afghanistan, witnesses said, killing at least two fighters and three civilians.

In one attack, gunmen opened fire on a Taliban vehicle at a local gas station in the provincial capital of Jalalabad, killing two fighters, a gas station attendant and a child.

A second child was killed and two Taliban fighters were wounded in a bombing of another Taliban vehicle.

A third attack, also a bombing of a Taliban vehicle in Jalalabad, wounded a person nearby but it was unclear if that person was a Taliban member or a civilian.

No one claimed immediate responsibility for Wednesday's attacks, although the so-called Islamic State group, which is headquartered in eastern Afghanistan, has said it was behind similar attacks in Jalalabad last week that killed eight people.

The Taliban and IS are enemies, and the attacks have raised the spectre of a wider conflict between the long-time rivals.