Afghan troops are seen in the Chardarah district of Kunduz province

Afghan forces have begun an operation to retake the city of Kunduz, which was seized by the Taliban on Monday.

Security forces have cleared the area around the central prison and the police headquarters, police spokesman Sayed Sarwar Hossini said. The US said it carried out an air strike on the city early on Tuesday.

Afghan troops and officials had retreated to the airport after militants overran the northern city and freed hundreds from jail. The attack came as President Ashraf Ghani completed a year in office.

It was one of the most significant militant assaults in years and will pile pressure on Mr. Ghani’s unity government – Kunduz is the first provincial capital seized by the Taliban since they lost power in the US-led invasion in 2001. But reporters say their main challenge will now be to hold the city.

The insurgent attack began at dawn on Monday as fighters fell upon the city from different directions. They captured key buildings and freed about 500 prisoners, including members of the Taliban, from the jail. (BBC)