In a video released by the self-proclaimed 'Islamic State' (IS) militants, 25 men were shown being executed by gunfire in the ancient city of Palmyra, Syria.

According to the BBC, ISIS said that these men were all soldiers, captured in Homs.

The gunmen who participated in the mass execution were all very young, around 13-14 years old.

IS seized the city of Palmyra and the neighboring city of Tadmur in late May.

In the undated video, the execution takes place at a historical site within the ancient city, in front of a large black flag of IS.

Approximately one hundred men in civilian clothes sat watching the murder. Among them were many minors.

The Syrian Human Rights Observatory in the UK claims that several such executions took place on May 27, but it is unclear whether these events were captured on video.

In a related development, a British family of 12 has joined IS.

Initial reports stated that the family had gone missing, but they later appeared with IS, and a statement in their name said they felt 'safer than ever'.

This family, including three young children aged 1-11, has been missing since May 17th. Police say they may have traveled to Syria.

(According to VNN)