Germany must urgently evacuate up to 10,000 people from Afghanistan for whom its has responsibility, Chancellor Angela Merkel told party colleagues, warning that the fallout from the conflict will last for a very long time.

"We are witnessing difficult times," Merkel told a closed-door meeting of her Christian Democrat party on Monday. "Now we must focus on the rescue mission."

The German leader said those needing evacuation included 2,500 Afghan support staff as well as human rights activists, lawyers and others whom the government sees as being at risk if they remained in the country, up to 10,000 altogether.

German Foreign Minister Heiko Maas said Germany was seeking to evacuate as many people at risk as it could, adding that NATO allies had misjudged the situation when they thought Afghan government forces could hold back the Taliban unaided.

"We want to get as many people out of the country as quickly as possible," Maas told reporters outside the foreign ministry.

(With input from Reuters)