An Iraqi soldier survived a mass execution committed by Isis by dropping to the floor after a bullet killed the man next to him and pretending to be dead.

Isis militants killed up to 1,700 men in mass executions at five locations in Tikrit after seizing the city in northern Iraq in June.

Forensic teams have now begun excavating suspected mass graves in Tirkit believed to contain the bodies, just days after Iraqi forces re-took the city from the clutches of Isis militants.

Ali Hussein Kadhim, a 23-year-old soldier who survived of one of the shootings, identified one of three newly discovered sites. His account of the massacre was one of the only to emerge.

He spoke in September after a report from Human Rights Watch (HRW) estimated that militants had killed over 700 men.

Mr Kadhim was captured on 12 June with thousands of other men at about 11am as they tried to flee along the main road from a military base. Soldiers and officers had advised him to wear civilian clothes to try to avoid detection by Isis fighters, but he was taken anyway.

Mr Kadhim said he was among prisoners held in a shipping container in a palace compound in the city before being taken out in a group of 10 at about 5pm, where the men were lined up to be shot with pistols one after another.

Militants tied their hands behind their backs and blindfolded them, then forced them to crouch forward with each man biting the t-shirt of the man in front as they marched them to the bank of the Tigris river.

He told HRW he survived by falling down and pretending to be dead when he was not hit by bullets. He then waited for hours before escaping under the cover of darkness.

A HRW spokesperson told The Independent he then hid in the reeds for days before he came into contact with HRW. In September, he was out of Isis-held regions and safe.

Speaking after the evidence was released, Peter Bouckaert, emergencies director at HRW, said the "barbarity" of Isis "violates the law and grossly offends the conscience".

Khalid al-Atbi, an Iraqi health official working with the forensic team exhuming the bodies in Tikrit told Reuters the findings were “heartbreaking”.

"We couldn't prevent ourselves from breaking down in tears,” he said. “What savage barbarian could kill 1,700 persons in cold blood?"