An Afghan official says hundreds of Taliban fighters have launched a new attack on a strategic northern city, storming it from several directions.

Sayed Sarwar Hussaini, the Kunduz provincial police chief's spokesman said Monday that the attack on the city started about 3 a.m. Battles with government forces are still underway in at least four locations, he says.

So far, about 20 insurgents have been killed with confirmed casualties among security forces but no figure, he says.

A tweet on a known Taliban Twitter account claimed responsibility. The tweet said all Kunduz city residents should remain indoors.

Kunduz province is on a strategic crossroads connecting the four points of Afghanistan. It has been the scene of intense insurgent attacks since April, with the Taliban joining forces with other insurgents.