The United Nations appealed for $4.4 billion in "unconditional" humanitarian aid for Afghanistan on Thursday, saying 9 million people faced famine and that families were selling children and organs to survive.

The humanitarian situation has "deteriorated alarmingly" since the Taliban takeover in August and the economy has "all but collapsed", U.N. Secretary-General Antonio Guterres said, opening the high-level pledging conference.

But in a nod to donors' concerns, he also called for the reopening of schools for all students in Afghanistan "without discrimination", after the Islamist rulers' decision to ban girls from secondary education.

"Some 95 percent of people do not have enough to eat. Nine million people are at risk of famine. UNICEF estimates that a million severely malnourished children are on the verge of death, without immediate action," he said in a video message.

"People are already selling their children and their body parts in order to feed their families," Guterres said, drawing on a report earlier this month by the World Food Programme.

U.N. aid chief Martin Griffiths, speaking from Doha after talks in Kabul this week, said: "I had the firm impression that the door for dialogue with authorities remains open, they want to find a constructive way to work with us.

"They don't necessarily know how to work with the international community, including the complex question of girls' education. I hope we can resolve this problem in the future."

At Indira Gandhi Children's Hospital in Kabul he had seen tiny malnourished children and newborns sharing ventilators. The level of human suffering left him "speechless", Griffiths said.

Ahead of the drive, Britain pledged 286 million pounds ($374 million) for Afghanistan, where six out of every 10 Afghans need aid, much of it food.

"We need to work through the UN to deliver real change for the Afghan people, upholding their rights and holding the Taliban to account," British Foreign Secretary Liz Truss said.

The U.N. says funds under the appeal - three times the amount requested in 2021 and only 13% funded so far - go directly to aid agencies and none are channelled through the de facto authorities who swept to power as the last U.S. troops withdrew.

Among the first pledges, Germany announced it would provide 200 million euros ($221.46 million) while Qatar said it would donate $25 million.

The United States pledged $204 million, the ambassador to the UN, Linda Thomas-Greenfield, announced.

"The Taliban will not control our humanitarian funding," she said.

(Additional reporting by Ghaida Ghantous in Dubai, Editing by William Maclean and Nick Macfie)