Reports from the southern Afghan province of Helmand suggest Taliban militants are close to overrunning the strategically important town of Sangin.
Helmand's governor, Mirza Khan Rahimi, insisted the authorities were still in control but his own deputy said that Sangin had been overrun.
The Taliban said they controlled most of the town and the main administrative building had been abandoned.
In the east, a Taliban attack near Bagram killed six US soldiers.
It was one of the deadliest attacks on foreign forces in Afghanistan this year.