In a video message to media, Farah Governor Taj Mohammad Jahid said the Taliban had blown up an army outpost after digging a 400-metre (0.25 miles) tunnel to access it from a nearby house. He added that one soldier had also been captured by the insurgents.
Two local officials, one speaking on condition of anonymity, said dozens of military including elite commando forces had been killed. Provincial council member Khayer Mohammad Noorzai said that around 30 had died in the attack and that the base was in the hands of the Taliban.
A Taliban spokesman did not immediately respond to a request for comment.