UN Secretary-General Antonio Guterres has called for an end to violence in Afghanistan amid fears of a new civil war now that the Taliban has seized power.

"I call for an immediate end to violence, for the safety, security and rights of all Afghans to be respected, and for adherence to Afghanistan's international obligations, including all international agreements to which it is a party," Guterres said in a report to the Security Council this weekend.

The document, obtained by AFP, has not yet been released publicly.

"I urge the Taliban and all other parties to exercise utmost restraint to protect lives and to ensure that humanitarian needs can be met," Guterres said.

The report was compiled as the mandate of the UN political mission in Afghanistan is scheduled to expire on September 17.

The UN says Afghanistan is mired in a humanitarian crisis affecting 18 million people, or half the population.

UN aid efforts can finance help for only 38 percent of the population, so the world body urgently needs nearly $800 million, the report says.

"I call on all donors to renew their support so that life-saving response is urgently scaled-up, delivered on time and suffering is mitigated," said Guterres, who has convened an international aid conference for Afghanistan in Geneva for September 13.

He also called on countries to take in Afghan refugees and refrain from deporting any they might already be hosting.

And in an allusion to the Taliban's brutal first stretch of rule from 1996 to 2001, Guterres said: "Reports of severe restrictions on human rights throughout the country are highly concerning, particularly accounts of mounting human rights violations against the women and girls of Afghanistan who fear a return to the darkest days."