Taliban fighters entered the northern Afghan city of Kunduz on Monday (October 3) almost exactly a year after they briefly seized it in their biggest success of the 15-year war, while heavy fighting in the south underscored the country's deteriorating security.

Sheer Ali Kamawal, commander of the 808 Tandar police zone in Kunduz, said the attack began at around midnight (1930 GMT Sunday) and fighting was going on in and around the city. Some Taliban fighters had entrenched themselves in homes.

The fighters appear to have slipped through a defensive security line set up around Kunduz, entering the city itself from four directions before clashes broke out, witnesses in the city said.

In Kabul, Brigadier General Charles Cleveland, spokesman for Afghanistan's NATO-led force, said it was ready to provide support if needed.

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.