The United Nations has said it needed close to €4 billion in aid for Afghanistan in 2022 to avert a humanitarian catastrophe and offer the country a future after 40 years of suffering.

In its biggest-ever single-country appeal, the UN said €3.9 billion was needed within Afghanistan, while a further €549 million was required to support the millions of Afghans sheltering beyond its borders.

The UN said 22 million people inside Afghanistan and a further 5.7 million displaced Afghans in five neighbouring countries needed vital relief this year.

"A full-blown humanitarian catastrophe looms. My message is urgent: don't shut the door on the people of Afghanistan," said UN aid chief Martin Griffiths.

"Help us scale up and stave off wide-spread hunger, disease, malnutrition and ultimately death."

A view from malnutrition department of Indira Gandhi Children Hospital in Kabul

Since the Taliban hardline Islamist movement seized control of Afghanistan in mid-August, the country has plunged into financial chaos, with inflation and unemployment surging.

Washington has frozen billions of dollars of the country's assets, while aid supplies have been heavily disrupted.

Afghanistan also suffered its worst drought in decades in 2021.

Without the aid package, "there won't be a future", Mr Griffiths told reporters in Geneva.

He said the appeal, if funded, would help aid agencies ramp up the delivery of food and agriculture support, health services, malnutrition treatment, emergency shelters, access to water and sanitation, protection and education.

An estimated 4.7 million people will suffer from acute malnutrition in 2022, including 1.1 million children with severe acute malnutrition.

Mr Griffiths said that without humanitarian aid, distress, deaths, hunger and further mass displacement would follow, "robbing the people of Afghanistan of the hope that their country will be their home and support, now and in the near term".

However, if international donors come forward, "we will see the opportunity for an Afghanistan which may finally see the fruits of some kind of security."

Mr Griffiths said the security situation for humanitarian organisations in Afghanistan was probably better now than for many years, adding that the staff in the ministries in Kabul largely remained the same as before the Taliban takeover.

He said the UN Security Council's move in December to help humanitarian aid reach desperate Afghans, without violating international sanctions aimed at isolating the Taliban, had made the operating environment for donors and humanitarians on the ground much more comfortable.