A 14-year-old boy has been brutally executed by Islamic State militants for allegedly missing Friday prayers.

The teenager's parents were forced to watch their son be beheaded after he was charged with apostasy in his home town of Jarablus in Syria.

The city's central mosque is a dominant force for ISIS in the region, with Friday prayers a focal point for preaching and promoting the group's self-proclaimed Caliphate.

News of the boy's execution was broken by local activist Nasser Taljbini who is opposed to the jihadist group. He told Syrian-based ARA News that an ISIS-controlled Sharia court ordered the teenager to be beheaded in public.

"Dozens of people attended the brutal execution, including the victim's parents who were forced to witness the beheading of their own son," he said.

Taljbini added: "ISIS is trying to prove that it is still powerful despite all the military defeats. The group is trying to terrorise people through conducting such public punishments."

ISIS' treatment of children and teenagers has been in the spotlight after the group released a number of videos depicting child jihadis carrying out executions.