Baghdad, Jun 24 (IANS/AKI): The Islamic State (IS) militant group has published a gruesome video purportedly showing over a dozen men being murdered in northern Iraq, including five alleged spies being drowned inside a cage in a swimming pool.

The 16 'spies' were drowned, beheaded or blown up using a rocket-propelled grenade, IS's media arm claimed in the seven-minute video, recorded with religious backing music.

Images showed the men being split into groups and dressed in orange jumpsuits to be murdered.

Five were seen being locked in a cage similar to that used to burn captured Jordanian pilot Muath al-Kasasbeh alive earlier this year.

The cage was then lowered into a swimming pool with underwater cameras that recorded the men drowning.

Four men were locked in a car that was blown up using a rocket-propelled grenade in the desert, and a third group of seven men were made to kneel as explosives were wound around their necks to decapitate them.

The undated video shows IS militants inspecting the corpses and body parts of the men after their horrific killings.

The executions allegedly took place in Nineveh province, part of territory seized by the group across swathes of Iraq and Syria.