Witnesses described how he was hauled out into a packed public square and executed in front of a 'huge crowd' as a warning to others to not to miss prayers at the mosque.

His trial, at which he was accused of apostasy, is said to have lasted only a few minutes before the horrifying sentence was handed down in the city, which has been held by the extremists since 2013.

Activist Nasser Taljbini told ARA News:  'The teenage boy, who faced charges of apostasy, was beheaded in front of a huge crowd in central Jarablus on Saturday.'

One witness, who wished to remain anonymous, added: 'Before carrying out the execution, a "Sharia" official read a statement issued by the "ISIS Sharia Court", vowing everyone who misses prayers at the mosque to face a similar punishment.'

Friday prayers are held at a mosque each week, a time for the community to come together and worship.

The horrifying act comes just days after it was revealed ISIS militants had forced a 12-year-old girl to shoot dead five women in another so-called 'execution'.

Horrifying act comes just days after it was revealed ISIS militants had forced a 12-year-old girl to shoot dead five women in another so-called 'execution'.

This massacre occurred in Nineveh Province, in northern Iraq on Wednesday, Alsumaria News reported.

A source said: 'This evening, a 12-year-old girl belonging to the ISIS executed five women, including a doctor who refused to medicate ISIS members that were wounded in a coalition bombardment, by firing squad.

'This execution is considered to be the first of its kind to be implemented by a small girl within ISIS.'

HB/V12