Taliban hardliners are accused of holding their fighters' families hostage in Kandahar after hundreds reportedly surrendered in Kunduz.
The Northern Alliance say they are close to finally taking Kunduz.
Streams of Taliban and al-Qaida troops have handed over their weapons outside the militia's last northern stronghold.
But Osama bin Laden's commanders are said to be holding the wives and children of hundreds of Afghan soldiers in Kandahar, their spiritual home, to force them to fight.
The families are reportedly heavily guarded in three compounds while their husbands and fathers are forced to swear on the Koran never to let opposition or US forces enter the southern city.
Three Pakistani fighters who escaped described "a reign of terror" by Taliban leaders and Arab members of bin Laden's al-Qaida terror group.
There is no way to confirm their account, but others who fled the city also spoke of tensions between the most radical Taliban and Afghan fighters contemplating surrender.
The three Pakistanis say they walked for four days through desert and hills to escape Kandahar and sneak back across the Pakistani border.
"We made a grave mistake by going there," said Abul Kalam, a 23-year-old former student from the University of Karachi.
"(Taliban leader) Mullah Omar's lieutenants and Arabs have told these Taliban that they would only be allowed to meet their wives and children once the war is over," said Ahmed.