ISIS child executing prisoners on the banks of the Tigris River in one of the biggest massacres ever committed by Islamic State fanatics

Harrowing new footage has emerged of a young boy executing prisoners on the banks of the Tigris River, amid one of the biggest massacres ever committed by Islamic State fanatics.

Filmed during the ISIS killing spree in Tikrit last year, the young boy is seen shooting at least two men in the head after adults have dragged the prisoners before him.

Ignoring prisoners’ pleas for mercy, the child grasps a pistol with both hands as he pulls the trigger. The men’s limp bodies are then cast into the water, which soon flows red with blood.

Images of the child executioner are just a small part of a graphic 22minute-long video released by the jihadis at the weekend.

It was recorded during the Speicher massacre last year – an atrocity which left an estimated 1,700 dead and ranks among the worst to have occurred in Iraq over the past decade.

Young men are seen falling from trucks and pleading for their lives before being lay down in shallow graves and sprayed with bullets.

Others are executed individually as the killings continue into the night and an excavator is required to shift piles of bodies.

In fact, the wholesale slaughter was so vast the graves used to bury the victims could be seen from space.

ISIS gunmen captured the Iraqi cadets at the Speicher military base near Tikrit and executed them at various locations, mostly in the city’s former presidential palace complex which was built by former dictator Saddam Hussein.

The video, posted on jihadist forums, shows many victims pleading for their lives, attempting to explain they had only just joined the security forces.

Around 600 bodies have been exhumed since government and allied fighters retook Tikrit from ISIS in April but many of the victims were dumped into the Tigris River.

An unidentified ISIS leader in military uniform is seen in the video released on Saturday.

He states: ‘This is a message I address to the whole world and especially to the Rafidha dogs, I tell them we are coming,’ he said, using the pejorative term ISIS employs for Shiite Muslims.

The video was released four days after a court in Baghdad sentenced 24 men to death by hanging over the Speicher massacre.

The trial lasted only a few hours, and the convictions were based mostly on confessions the defendants claimed were obtained under torture.