A US soldier killed during an ambush in Niger was discovered by villagers with his arms bound and a major wound to the back of the head, a report said Friday.

The remains of Sgt. La David Johnson, who died during the October ambush in the West African nation, suggested he may have been executed by militants aligned with ISIS, The Washington Post reported.

Johnson’s body wasn’t found until two days after the attack.

A 23-year-old farmer told the paper that some children in the village were tending cattle when they made the gruesome discovery about a mile from the ambush site.

When the farmer arrived at the location, he saw Johnson’s body lying face down, his wrists tied and the back of his head “smashed in with something.”

The condition of Johnson’s remains suggested that he had been captured by the militants and likely tortured before he was killed, a village elder said.

“The back of his head was a mess, as if they had hit him with something hard, like a hammer,” the elder told the paper. “They took his shoes. He was wearing only socks.”

The elder added: “His two arms were tied behind his back.”

Villagers also said they saw the bodies of three other American soldiers — Staff Sgts. Bryan Black, Jeremiah Johnson and Dustin Wright. All three had been declared killed in action.

The body of one was slumped inside a pickup truck while the remains of the other two had been left on the ground.

The bodies were clothed in T-shirts and boxer shorts but it was not clear if the militants had stripped off the uniforms, the paper said.

The Oct. 4 botched military operation that resulted in the four deaths is under investigation by the Pentagon after US officials demanded more ­details.

The slain soldiers were preparing to leave a meeting in near the town of Tongo Tongo when they came under attack by about 50 militants armed with with grenades and machine guns.

The US military has been training soldiers in Niger since the early 2000s to help strengthen the country’s military.

The death of Johnson became a national controversy when his widow received a call from President Trump that she said left her in tears.

Myeshia Johnson claimed Trump could not remember her husband’s name during the call and told her “he knew what he signed up for . . . but when it happens, it hurts anyway.”