"Those two girls were evil and they were spies for the enemy (the Somali government), but the mujahedeen caught them and after investigation, they admitted their crime, so they have been executed," said Sheikh Yusuf Ali Ugas, commander of Al-Shabaab in Beledweyne, a town in central Somalia.
The teens were blindfolded with their hands behind their backs against a tree, and shot, according to a local journalist.
A resident of Beledweyne told CNN that Al-Shabaab called on the town's residents to come out and watch the execution.
"Hundreds of people came out to watch the execution," he said. "It was very bad ... the girls looked shocked and were crying but [no one] could help."
A relative of one of the teens denied they were spies.
"My cousin, Ayan Mohamed Jama, was just 16 years old and she was absolutely innocent," said the relative, who did not want their name used out of fear of retribution from Al-Shabaab. "And Al-Shabaab caught her and the other girl between El-gal and Beledweyne and simply accused them of what they were not."
The other girl, said the relative, was 15. Al-Shabaab refused their families' request to see the teens while they were in detention, "and they executed them at a public gathering, so this is inhumane and cruelty."