Taliban fighters conducted an early morning attack on Afghanistan's northeastern province of Kunduz and seized most of it after entering the area from three different points.
Taliban seized the provincial governor's office in the city, raided prisons and freed hundreds of inmates.
Afghan government confirmed that "most of Kunduz city has fallen to the Taliban," and troops were retreating to the airport.
"Our fighters are now advancing toward the airport," Taliban spokesman Zabihullah Mujahid said on Twitter.
The streets of the city were abandoned as the residents kept themselves indoors.
A Western NGO official told the AFP news agency that "The situation is very bad. The fighting is particularly fierce in the southeastern area of the city."
On Sunday a bomb attack was carried out on a sports field in Paktita that left nine dead and dozens injured. No group has yet claimed responsibility for the attack.
Also on Sunday, a group claiming to be allied with ISIS conducted an attack on a checkpoint in Nangarhar located east of the city which is very close to the capital city Kabul.
The Taliban has been waging an armed struggle against the Afghan government since it was ousted from power by US-led invasion in late 2001. Attacks by the group gained momentum during a summer offensive launched in April against the Western-backed government in Kabul.
Afghanistan’s NATO-trained security forces are fighting against Taliban fighters without much direct support foreign forces many of which left Afghanistan after finishing their mission in 2014.
According to a UN report, the civilian death toll from attacks in the country has reached new highs after a peace initiative led by President Ashraf Ghani over summer ended with failure.