Pictures released by ISIS (Islamic Sate, ISIL , IS and DAESH) show the young man fall to his death in front of a large crowd, including dozens of children.
Residents in Manbij had been ordered to gather below to witness the execution of a man convicted of 'sodomy', ARA News reports.
The images show ISIS terrorists standing on the roof of a building under construction in central Manbij city with their young victim blindfolded, barefoot and bound in front of them, Daily Mail reports.
They push the man off the building, after which his corpse is stoned by the baying mob in the streets below.
'The man was thrown brutally by ISIS masked members from the top of the building in the city. The barbaric execution took place in front of hundreds of people,' media activist Nasser Taljbini told ARA News.
ISIS has previously publicly executed men in a similar manner for being found guilty of homosexuality. Most of victims is ISIS opponents.