Taliban fighters have attacked the northern city of Kunduz overnight and are battling government forces on the streets.
Sheer Ali Kamal, commander of the 808 Tandar police zone in Kunduz, said the attack began just after midnight on October 3 and added that militants entered the city from several directions.
Kamal said fighting was ongoing.
An AFP correspondent said there was "intense fighting" between the Taliban fighters and the government forces.
"We are putting all our efforts together to push them back," Kamal said.
Kunduz fell for a few days to the Taliban one year ago in a battle the UN said left 289 people dead and hundreds more wounded.
Kunduz has been attacked on several occasions by the Taliban since then and was seriously threatened in April.
A Reuters reporter said he saw Taliban fighters armed with AK-47 assault rifles, machine guns, and rocket-propelled grenades in the city.
Two Afghan army helicopters were also seen flying over the city, which was deserted.
The attack comes as the Taliban has undertaken assaults in several parts of Afghanistan, including the southern Helmand Province and its capital, Lashkar Gah.