MOGADISHU, Somalia (AP) — Somalia’s most powerful militant group publicly executed three of its members Sunday, saying the trio had spied on the militants for the U.S. and British intelligence agencies.

Al-Shabab said the three men were CIA and MI6 informants, and were the reason several drone attacks killed leaders from the group.

Mohamed Jama, a resident in the coastal town of Merca, told The Associated Press that dozens of masked fighters tied up the three men and killed them by firing squad.

A self-proclaimed militant judge gave the death penalty order. Hundreds of residents were forced to watch and many of them vomited after the killings, Jama said.

“The execution and the verdict were quick and dirty. It was gruesome to watch,” he said. “The men instantly died after their bodies were riddled by bullets.”

A U.S. Embassy spokesman said he was not aware of the executions, but that in general the U.S. does not comment on intelligence matters.

An al-Shabab member, who gave his name as Abu Abdalla, said militants interrogated the men for six months before the executions.