The U.S. drone strike was intended to hit an Islamic State hideout in Afghanistan.
But instead it killed at least 30 civilians resting after a day's labor in the fields.
The attack Wednesday (September 18) night also injured another 40 people after accidentally targeting farmers and laborers.
They'd just finished collecting pine nuts in eastern Afghanistan.
A tribal elder said the workers had lit a bonfire and were sitting together when a drone targeted them.
A senior U.S official in Kabul confirmed the drone strike, but did not share details of civilian casualties.
Jihadist IS fighters first appeared in Afghanistan in 2014 - the U.S estimates there are around 2,000 Islamic State fighters in country.
There's been no let-up in assaults by Taliban and IS as Afghanistan prepares for a presidential election this month.
At least 20 people died in a Taliban truck bomb in southern Afghanistan Thursday (September 19).
Casualties are expected to rise as rescuers sift the rubble.
The militants wanted to target a training base for Afghanistan's powerful National Directorate of Security.
But parked the vehicle full of explosives outside a hospital gate nearby, a defense ministry source said.
The Taliban have been carrying out nearly daily attacks since the collapse of peace talks with the U.S. this month.