The attack began around midnight, with the insurgents capturing one district and parts of another, local provincial council member Jamila Amini told AFP Tuesday from inside the city.

"Heavy fighting continues inside the city and aircraft have just started bombarding Taliban positions," she said.

The insurgents released a statement warning residents to remain inside their homes and called on people to "stay calm".

But the defence ministry said the army had repulsed the attack, and "the security forces are now chasing the enemy".

"The sounds of explosions and gunfire have filled the city," one resident who gave his name as Bilal said, adding that he could see smoke rising from the direction of a building housing the Afghan intelligence service.

The assault comes as the Taliban are stepping up their spring offensive, in an apparent rejection of a peace talks overture by the Afghan government.

Farah is a poppy-growing province in a hard to reach part of Afghanistan which a section of the multi-billion-dollar TAPI (Turkmenistan, Afghanistan, Pakistan and India) gas pipeline will traverse.

It has been the scene of intense fighting in recent years.

In 2017 insurgents tried to overrun the capital three times, according to the Afghanistan Analysts Network.