The Taliban say they have taken control of Panjshir province north of Kabul, the Afghan capital, giving them complete control of Afghanistan.
The province was the last holdout of anti-Taliban forces in the country and the only province the Taliban had not seized during their sweep last month.
Thousands of Taliban fighters overran eight districts of Panjshir overnight, according to witnesses from the area.
Taliban spokesman Zabihullah Mujahid issued a statement saying Panjshir was now under the control of Taliban fighters.
"We tried our best to solve the problem through negotiations, and they rejected talks and then we had to send our forces to fight," Mujahid said Monday.
The anti-Taliban fighters had been led by the former vice president and the son of the iconic anti-Taliban fighter Ahmad Shah Massoud, who was killed just days before the 9/11 attacks in the United States.
The Taliban have been in control of Afghanistan since Aug. 14, when forces overtook the U.S.-backed Afghan National Security Forces and claimed the city of Kabul.
The Taliban's resurgence came as U.S. forces evacuated Afghanistan ahead of a White House-imposed Aug. 31 deadline. The departure from the country marked the end of the 20-year Afghanistan War, the longest war in U.S. history.