An Afghan government negotiator on Thursday said the Taliban had offered a three-month ceasefire in exchange for the release of 7,000 insurgent prisoners, as the militant group continues a sweeping offensive across the country.

“It is a big demand,” Nader Nadery said, adding that the insurgents have also demanded the removal of the Taliban's leaders from a United Nations blacklist.

A senior insurgent leader had said on Tuesday that the Taliban do not want to battle government forces inside Afghanistan's cities and would rather see them surrender.

The hardline group has swept through much of the north as foreign troops complete their withdrawal, and the Afghan government now holds little more than a constellation of provincial capitals that must largely be resupplied by air.

As security deteriorates, France on Tuesday became the latest country to call on its citizens to leave — offering them a last flight out of Kabul, free of charge, on Saturday.

Earlier, the head of a Taliban commission that oversees government forces who surrender had urged residents of Afghanistan's cities to reach out to them.

As foreign forces wind up their withdrawal — due to be completed by August 31 — the situation on the ground is changing rapidly.

The top US general in Afghanistan relinquished his command on Monday at a ceremony in the capital, the latest symbolic gesture bringing America's longest war nearer to an end.

The pace of the pullout — and multiple offensives launched by the Taliban — have raised fears that Afghanistan's security forces could be swiftly overwhelmed, particularly without vital US air support.

Around 650 American service members are expected to remain in Kabul, guarding Washington's sprawling diplomatic compound.