A Yazidi refugee and his two nephews have told how they had to play dead to survive after they were rounded up, forced to stand next to a ditch and shot by laughing ISIS soldiers in a massacre which killed 800.

Once ISIS overran their town last August, the Yazidis were herded into a school and their armpits were inspected.

The women and girls were put on one side of the hall, to be taken away as sex slaves, while the men were lined up on the other.

Those with underarm hair were judged to be older than ten - and old enough to be murdered.

The 'men' were then split into two groups; those willing to convert to Islam and those who wanted to remain Christians.

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Massacre: The Yazidi men and boys were rounded up in front of a mass grave outside Kocho village and shot

Slaughter: The men were lined up in a ditch and shot in the head by laughing ISIS gunmen. A survivor told how he played dead while covered in victims' blood and hid among the dead bodies

Lucky to be alive: Yazidi massacre survivor Jamal was shot in the neck, the shoulder, causing him to fall into the grave alongside other bodies

Bullet wounds: Kameel was shot four times - twice in his right hand, and once in the arm and leg - during the massacre in a field outside the village of Kocho, northern Iraq

The Christians were told that they would be taken to the Sinjar mountains and freed.

But it was a trick – and instead they were put into trucks and taken to killing fields around the village of Kocho, northern Iraq, where they were made to stand by mass graves and executed.

Khalaf – whose name has been changed to protect his identity – told how he was one of 800 men shot at, but survived.

He was too scared to move or even breath as he laid, covered in blood from other victims, as dead bodies fell on top of him.

Khalaf’s two brothers were murdered that day, but his two nephews Kameel and Jamal, again, not their real names, lived by laying in the grave for hours while soldiers walked along checking for survivors.

If they found anyone still alive they were shot in the head to be sure they were dead.

A man lying next to Khalaf in the ditch was found by an ISIS fighter to still be breathing, so he was shot three times in the head.

Speaking from a refugee camp in Iraq, Khalaf, 42, told MailOnline: 'They [ISIS] took everybody to the big school inside Kocho. They took everything from us – telephones, money, gold.’

The jihadis ordered men and boys over the age of 10 to stand on the right and women and other children on the left.

'They tested to see if the boys had underarm hair,' he said.

The fanatics used this crude test to determine whether the Yazidi boys were old enough to be slaughtered.

In what appeared to be an act of humanity, the fighters gave around 400 men and boys standing on the right-hand side a choice - to become a Muslim or be led to Mount Sinjar where they would be set free.

'They did not say anything bad [to us],' Kameel, 32, said. 'They said if you want to stay and be a Muslim it is ok. If you want us to take you to the mountain, we will and you can leave.'

Execution: Men are made to kneel before being shot by Islamic State gunmen in Raqqa province, Syria. This is not the Yazedi mass grave execution, but a similar incident

Death: Human skulls were found in a mass grave on the outskirts of the town of Sinjar where police said the grave contained remains from 25 people belonging to the minority Yazidi sect, killed by Islamic State militants

Chilling memories: Khalaf, Kameel and Jamal have spoken to MailOnline from this refugee camp in Iraq

Gunshot: After falling into the grave, Jamal was shot a further two times - in the leg (pictured) and stomach

Survivor: Jamal was shot in the shoulder and the neck and then a further two times - in the leg and abdomen

Injured: Kameel shows MailOnline a gunshot wound on his arm at a refugee camp in northern Iraq

Most chose to leave and were led to trucks in groups and driven to fields outside the village.

Khalaf, his nephew Kameel, and his two brothers were in one of the first convoys and they were driven about 500 metres out of the village. It was there that they saw what ISIS had planned for them.

'They lied,' Khalaf shouted, unable to contain his anger as he recalled the terror. 'On the way there [we saw] there was a mass grave – they had prepared everything.

'They had dug the grave and set up the machines guns.'

The jihadis - some Iraqis from neighbouring towns - told their helpless captives to stand and face the ditch.

'I was first in line they started shooting at us,' Khalaf recalled. 'Then they observed if we moved, [if we did] they shot at us again.

'In our group there was about 40 of us, with me was two of my brothers and my nephew.'

Khalaf's brothers were killed during the massacre, but miraculously he managed to escape with only bruises.

Kameel - who was only a few places down the line - also survived despite being shot four times.

'I was hit with two bullets in my right hand, another in my arm and then one on my foot,' he said, showing his scars.

After the initial hail of bullets, both men were too scared 'to open their eyes' or even breathe for fear that ISIS would find out they were still alive.

'ISIS checked one man beside me,' Khalaf explained. 'They found he was breathing and shot him three times in his head.'

Meanwhile, Khalaf’s other nephew, Jamal, 31, was heading to a different killing field.

'You have to relax, we will give you water,' he recalled being told by an ISIS fighter as they drove there.

However, when he arrived he also realised what they had planned - there was a grave surrounded by ten armed jihadis ready to kill.

Jamal remembers overhearing one Arabic fighter joking: '80 or 90 Yazidis is enough for this grave.'

This time the Yazidis were forced onto their knees, before being shot down one by one with their machine guns.

'I was shot in the shoulder and the neck,' Jamal, a father-of-two, recounted. 'I fell straight into the grave. Then I was shot in my leg and my abdomen.'

Fearful, like his cousin and uncle, that ISIS would discover he was still alive, he held his breath and closed his eyes.

After 30 minutes the jihadis had left and Jamal raised his head and was confronted with a disturbing scene.

ISIS overran Kocho, in northern Iraq, killing men and boys and burying them in mass graves last August. The survivors, including Khalaf, Kameel and Jamal, escaped to Mount Sinjar. From there, Kameel and Jamal were airlifted to Zakho, and the three relatives spoke to MailOnline from a refugee camp in Duhok

Speaking from a refugee camp in Iraq, Khalaf, 42, told MailOnline: 'They [ISIS] took everybody to the big school inside Kocho. They took everything from us – telephones, money, gold.’

MailOnline spoke to the three men (not pictured) at a refugee camp in northern Iraq on the condition of anonymity

Hidden away: Yazidis who fled the violence from ISIS forces in Kocho set up shelter on Mount Sinjar last year

'The person next to me was dead,' he said. 'He had been shot through the top of his head. The bullet had come out of his neck. His blood was all over my body.'

The three surviving family members made their way to Mount Sinjar separately.

Khalaf – the least injured – initially tried to help his fellow Yazidis, including his nephew by giving them water. Then, he decided to head to a nearby field with two teenage boys.

'During the day we hid in this field, and then at night we headed to Sinjar Mountain,' Khalaf said.

His two nephews had a more difficult escape.

'I was in a lot of pain,' Kameel said as he rubbed his now-deformed foot. 'However, I tried to ignore it.'

He too managed to make it to Sinjar Mountain, where he spent five days with no medical treatment, before being airlifted 150 miles to Zahko to be treated for his injuries.

His younger cousin, Jamal, whose injuries were more severe, including a bullet still lodged in his neck, crawled from his mass grave before fleeing to the mountain.

'[One] man did help me into his tent...[but] nobody gave me any water because they thought I was going to die,' he recalled.

He spent six days on the mountain before he too was airlifted to safety.

'When I made it to Zahko I was in hospital for four days, where they removed the bullet from my neck,' he said.

For these three family members the ordeal is not over. They believe ISIS has killed at least 17 of their relatives and still has about 30 in captivity.

'My wife and two children are still with ISIS in Syria,' Jamal conceded. 'But, I'm working on smuggling them to safety soon.'

Tens of thousands of Yazidis fled in August when ISIS captured the Iraqi town of Sinjar.

About 50,000 Yazidis - half of them children, according to U.N. figures - escaped to the mountains outside during the onslaught.

Hundreds were taken captive, with some Yazidi women forced into slavery, according to international rights groups and Iraqi officials.

The women and girls abducted from the village were being taken to the ISIS-controlled cities of Mosul and Tal Afar, an official said.

It came as jihadis vowed to impregnate hostages in their furious bid to convert all non-Muslims.

The US launched air strikes and humanitarian aid drops in Iraq on August 8, partly in response to the crisis on Sinjar Mountain.