Local anti-IS activist group, Raqqa Is Being Slaughtered Silently, claims 13 boys were rounded up and publicly shot by a firing squad using machine guns.

"The bodies remained lying in the open and their parents were unable to withdraw them for fear of murder by terrorist organisation," the activists’ website reported.

The “crime” of the young group was said to be “breaking religious laws by watching the football”, which was announced via loudspeaker before the boys were killed.

While international news agencies have yet to confirm the story, Jordanian news agency Petra and other Iraqi sources were sourced.

The Group D match, which Iraq won 1-0 thanks to a goal from Yaser Kasim, was played in Brisbane last Monday, 12 January. It’s unclear when the alleged execution took place, but reports of the horror surfaced overnight, one week after the match had been played.

IS now controls some parts of Iraq, including Mosul and Fallujah, and has also taken control in many parts of Syria, including the city of Raqqa, from which the activists working against the regime took their name.

Raqqa Is Being Slaughtered Silently has taken to documenting the brutal regime of IS at great risk to its members.

One of them, Abu Ibrahim Raqqawi, recently told VICE News: “We were activists against the Assad regime when we started, but after our city was freed, and ISIS took over our freedom, we just decided to launch this campaign to expose all the crimes that ISIS do.”

For more news on the conflict involving IS, visit SBS News.