Afghans pouring into Kabul and those still in the Taliban-held areas say that they have witnessed unprovoked attacks on civilians and executions of captured soldiers.

In addition, they say, Taliban commanders have demanded that communities must hand over unmarried women to become "wives" for their fighters — a form of sexual violence, human-rights groups say, the Wall Street Journal reported.

The US Embassy in Kabul had said on Thursday that it had received reports of the Taliban executing members of the Afghan military who had surrendered. "Deeply disturbing and could constitute war crimes," the Embassy said. A Taliban spokesman, Zabiullah Mujahid, denied that the group had killed any prisoners, saying that would violate their principles.

He also said that allegations that the Taliban were forcing women into marriage were false, and that such actions would be contrary to the rules of Islam and violate cultural tradition.

On Wednesday, Mawlawi Abdul Qadir, a senior Taliban religious official, had said in a speech in the newly captured capital of Badakhshan province that government soldiers who surrender and "confess their crimes" would be able "to live like a Muslim under the flag of the Islamic Emirate".

Taliban leaders have publicly pledged to be magnanimous in victory, assuring government officials, troops and the people of Afghanistan that they have nothing to fear as ever larger swaths of the country fall under their control.