The Taliban has taken over central Kunduz but government forces were still in control of the city’s airport, said a spokesman for the group.
Footage posted on social media showed Taliban fighters in the center of the city.
Sheer Ali Kamawal, commander of the 808 Tandar police zone in Kunduz, said the Taliban assault began at around midnight on Sunday and fighting was going on in and around the city. Some Taliban fighters had entrenched themselves in homes.
The fighters appeared to have slipped through a defensive security line set up around Kunduz, entering the city from four directions before clashes broke out, witnesses said.
In Kabul, Brigadier General Charles Cleveland, spokesman for Afghanistan’s NATO-led force, said it was ready to provide support if needed.
“At this point, we are not observing evidence via our internal means to support the reports that Kunduz is under significant attack,” he told Reuters in an emailed statement.
With fighting intensifying across the country, the attack on Kunduz, a day before a major donor conference in Brussels, underlined Afghanistan’s precarious security situation and the Taliban’s ability to strike against important targets.
Government forces, fighting with limited NATO-force support following the end of the main international combat mission in 2014, are estimated to have control over at most two-thirds of the country.
In Kunduz, police spokesman Mahfozullah Akbari said security forces were preparing to drive out the fighters, who had infiltrated the Khak Kani area in the city’s southwest.
“The Taliban are inside some civilian houses and we have to carry out operations very carefully,” he said.
Military helicopters flew overhead and gunfire could be heard in Kunduz, where a year ago to the day, Afghan troops backed by US air strikes and Special Forces were battling to drive out Taliban who had raised their flag in the city center.
Residents piled into cars and trailers to escape the city center and shops were shut. Several checkpoints were burned out but there was little actual fighting as security forces held back from confrontation in the city center.
Witnesses, however, saw Taliban fighters armed with AK-47 assault rifles, machine guns and rocket-propelled grenades walking around the deserted streets of the city, entering homes and taking up position on rooftops.
Taliban spokesman Zabihullah Mujahid said on his official Twitter account that four government checkpoints in Kunduz had been captured and some soldiers had been killed.
“A massive operation started on Kunduz capital from four directions early this morning,” he said.
Attacks across Afghanistan
The assault on Kunduz came as the Taliban have stepped up attacks in different parts of Afghanistan, including the southern province of Helmand, where they have been threatening the provincial capital of Lashkar Gah.
On Monday, Taliban fighters, positioned just across the Helmand River from the center of Lashkar Gah, also took control of Nawa district to the south, killing a district police chief, officials said.
Heavy fighting has also continued along the main road to Tarin Kot, the provincial capital of Uruzgan, also in the south, where a Taliban raid on September 8 sparked fears of another collapse like that in Kunduz last year.
The raid on Tarin Kot was beaten back but alarmed security officials because the militants were able to enter the city without significant resistance after police abandoned dozens of checkpoints.
The fall of Kunduz last year was one of the most serious blows suffered by the Western-backed government in Kabul since the withdrawal of most international troops in 2014.
Although the insurgents abandoned Kunduz after a few days, the capture of a provincial capital underlined their growing strength and exposed flaws in Afghan security forces and the city has remained effectively besieged ever since.
“Every day the militants come to the city and are pushed back by security forces,” said Amruddin Wali, a member of the provincial council, as he stood with security forces on the edge of the city. “There is killing and fighting every day.”
Efforts at reviving peace talks with the Taliban have failed to produce results but Afghanistan’s international partners are expected to approve maintaining billions of dollars in funding for the government over the next four years at a two-day meeting in Brussels this week.