Ali is seen here in the crowd of captured Iraqis by the Islamic State. Islamic State

An Iraqi soldier survived a mass execution at the hands of Isis (now known as the Islamic State) by playing dead, in what is one of the few inspiring stories to emerge out of the terror group's march across northern Iraq.

Following its capture of the city of Tikrit, the home town of former Iraqi dictator Saddam Hussein, the Islamic State captured and killed approximately 770 men in mass killings at five different locations, according to Human Rights Watch.

However, Ali Hussein Kadhim - an Iraqi soldier and a Shiite - managed to escape the bloodbath after the men were lined up in groups and fired at one by one.

The firing squad shot a man next to Ali and blood splashed onto his face. Ali was next but the bullet intended for him passed his head and he fell to the ground as if he had been killed.

"I saw my daughter in my mind, saying, 'Father, father,' " he told the New York Times. "I just pretended to be shot."

After he fell forward into the ditch which the militants had prepared for the Shiites, a militant inspected the bodies and saw that a fellow soldier of Ali's was still alive.

"Just let him suffer," said another militant. "He's an infidel Shia. Let him suffer. Let him bleed."

"At that point, I had a great will to live," said Ali. He proceeded to wait four hours before fleeing in the dark to the Tigris River - 200 yards away.

When Ali reached the river, hiding among the reeds, he met with another injured man named Abbas, who had been shot by IS militants and pushed into the river. The pair remained at the riverside for three days due to Abbas' injuries, eating whatever was available to them.

"It was three days of hell," said Ali. He had to leave Abbas, embarking on a three-week journey through Sunni Iraq to reach safety, which Human Rights Watch has confirmed.

While HRW have confirmed the death of at least 770 men, IS have claimed to have killed over 1,700 Shiite soldiers in the massacres in Tikrit and are believed to be holding hundreds of other soldiers hostage.

The UN's Deputy Human Rights Commissioner, Flavia Pansieri, has said that IS has committed targeted killings, forced conversions, sexual abuse and slavery in Iraq.

Pansieri added that Christian, Yazidi, Turkmen, Shabak, Kaka'i, Sabeans and Shia communities had "all been targeted through particularly brutal persecution" in "what may amount to ethnic and religious cleansing".

According to the UN's figures, over 1.6 million people have been displaced by conflict in Iraq this year while 850,000 people fled their homes in August alone.