The Taliban have told Germany that Afghans with legal documents will be able to travel on commercial flights beyond the August 31 cut-off date, after which evacuations from Kabul airport will no longer be allowed, a senior German diplomat said on Wednesday.

"Director Stanekzai assured me that Afghans with legal documents will continue to have the opportunity to travel on commercial flights after August 31," German envoy on Afghanistan Markus Potzel, who is negotiating with the Taliban in Doha, said on Twitter.

Sher Mohammad Abbas Stanekzai is the head of the Taliban's political office in Doha.

"We talked about the urgent need for a functioning airport in Kabul as a prerequisite for [a] diplomatic & NGO presence" in Afghanistan, Potzel, who has been negotiating with the Taliban extensively in the past, added.

The Taliban have asked Turkey for technical help to run Kabul airport after the departure of foreign forces but insist that Ankara's military also withdraw fully by the August 31 deadline, reported Reuters, citing two Turkish officials.

The Turkish defense ministry on Wednesday said it had started to evacuate its troops from Afghanistan. 

The Kabul international airport is being guarded by U.S. and British troops.

(With input from Reuters)