Afghan forces retook control of the strategic northern city of Kunduz on Thursday after a three-day Taliban occupation that dealt a stinging blow to the country’s NATO-trained military.

Afghan forces retook control of the strategic northern city of Kunduz on Thursday after a three-day Taliban occupation that dealt a stinging blow to the country's NATO-trained military.

The fall of the provincial capital, even temporarily, highlights the stubborn insurgency's potential to expand beyond its rural strongholds in the south of the country.

Afghan forces, hindered by a slow arrival of reinforcements but backed by US air support, struggled to regain control of the city after three days of heavy fighting.

But on Thursday Afghan forces managed to reach the center of Kunduz where the streets were littered with Taliban bodies, Kunduz residents told AFP, adding that fighting was still ongoing in parts of the city.

Deputy Interior Minister Ayoub Salangi said the city had been recaptured after a "special operation" overnight.

Local residents reported deafening overnight bombardments, adding that the Taliban were still resisting Afghan forces in some parts of the city.

"Afghan soldiers took down the white-and-black Taliban flag in the city square and hoisted the government flag," Kunduz resident Abdul Rahman told AFP.

"The Taliban suffered heavy casualties last night. Dead bodies are scattered on the streets, and their supporters are carrying them out of the city wrapped in white cloths."

The Taliban stepped up attacks during a summer offensive launched in late April against the Western-backed government in Kabul.

After years of costly involvement, most NATO troops pulled back from the front lines by the end of 2014, although a residual force of around 13,000 remains for training and alleged counter-terrorism operations.