When the Taliban won back control of the eastern Afghan province of Nangarhar last month, they set out to settle a score with an old foe.

Prominent local politician Ajmal Omar helped drive the Taliban out of a Nangarhar district a year earlier and tried to dissuade young Afghans from joining them.

As they searched for Ajmal, Taliban members detonated explosives at his ancestral home.

They also looted gold and cars, and detained and whipped several of his relatives to try and establish his whereabouts.

The events were recounted by two relatives who say they were targeted in the reprisals.

Also sharing their stories were 10 local officials, residents who witnessed or were familiar with the incidents and a former Afghan intelligence official...