Sadistic ISIS fanatics are turning children into an army of hundreds of murderous monsters willing to blow themselves up, die in battle and execute hostages for their twisted cause.

Extremism experts warn children are being indoctrinated and radicalised from birth, leading to a 'whole generation who will know nothing other than ISIS ideology'.

Their comments follow the release of a sickening new video that purports to show a boy of about 10 years old shooting dead of a 19-year-old Israeli-Arab who was taken hostage by the terror group.

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Training: Video footage released by the terrorist organisation shows children carrying guns during a training session

Armed: The children learn to fire AK-47s under the guidance of Islamic State militants in an unnamed training school

Young jihadi: It seems there is no age limit to attend an Islamic State school where children are 'brainwashed'

Footage purports to show the child raise his gun and aim it at Muhammad Said Ismail Musallam's forehead before shooting him at point blank range

Vile: A new video appears to show a boy of about 10 years old shoot an Islamic State hostage in the head

The footage appears to show the child, now believed to be a French citizen, raise his gun and aim it at Muhammad Said Ismail Musallam's forehead before shooting him at point blank range.

The hostage seems to be shot a further three times on the ground before the boy lifts his gun to the sky in celebration, shouting 'Allahu Akbar!' and appearing to fire one final shot.

The footage of a child seemingly carrying out such a brutal execution has sent shock waves around the world, but it came as no surprise to experts who have been following the brainwashing of youngsters by ISIS.

Charlie Winter, a researcher at the Quilliam Foundation, a counter-extremism think tank, said: ‘It is something that has been going on for a long time now.

'It’s deeply, deeply worrying because these children are growing up without any outside influence.

‘They are kids that are being indoctrinated and radicalised from birth.'

He added: ‘This is going to be a long-term problem – there is going to be a whole generation of kids in Northern Iraq and Eastern Syria who will know nothing other than Islamic State ideology.

‘I don’t think there is a choice in it for the children – they are the biggest victims in all of this.’

‘I don’t think there is a choice in it for the children – they are the biggest victims in all of this,' said an expert

Indoctrinated: These children are learning to become Islamic State militants at a school run by the terror group

Combat training: Videos released by the group reveal the tough military training children are forced to undergo and the warped curriculum they learn in terrorist-run schools

Two boys wrestle on the floor at an Islamic State training school, where they are also taught to fire AK-47s

ISIS video claiming to show a young boy executing two Russian spies - Mamayev Jambulat Yesenajovich and Ashimov Sergey Nikolayavich

But how does ISIS turn these innocent children into bloodthirsty killers, and how is it able to so effectively?

Videos released by the group reveal the tough military training children are forced to undergo and the warped curriculum they learn in terrorist-run schools.

Last month, ISIS released a slickly-edited propaganda video showing boys as young as five being indoctrinated at a military-style training camp for 'cubs' in Syria.

I don’t think there is a choice in it for the children – they are the biggest victims in all of this Charlie Winter, Quilliam Foundation researcher

Children are said to be taught how to use weapons and even show how to behead using dolls.

'They teach them how to use AK-47s,' an Iraqi security official told NBC News.

'They use dolls to teach them how to behead people, then they make them watch a beheading, and sometimes they force them to carry the heads in order to cast the fear away from their hearts.'

Other footage shows children being taught in an ISIS school before learning hand-to-hand combat and how to fire a gun.

Pictures posted on ISIS-linked social media accounts have included babies posing with firearms and young children holding up the heads of beheading victims.

Some propaganda videos attempt to show the 'lighter' side of life under the control of the caliphate, and unsophisticated ploys such as giving sweets to children seem to have played a part in the radicalisation.

ISIS-branded clothing has been made for children and even newborn babies.

In a nine-minute video, children in camouflage are seen being trained at the Farouk Institute for Cubs, in the Raqqa province in Syria

'Teacher': In footage released by ISIS, this man teaches a group of children to write Arabic in a classroom

Unsophisticated ploys such as giving sweets to children seem to have played a part in the radicalisation

Islamic State hands out sweets to children in Benghazi, Libya - another ploy to attract even younger recruits

Human Rights Watch, an organisation which defends the rights of people worldwide, interviewed four former ISIS child and adult fighters, as well as civilians in the terrorist-controlled areas in Syria.

It found the militants have actively recruited children to send to military training camps and have used them in operations including suicide bombings.

Barbaric: A child holds a severed head in a photograph too gruesome to show

The children, including Bassim, 17, who joined at just 16 after attending ISIS sermons, said they were recruited through public forums.

Raed, 17, went to a training camp when he was just 16, after ISIS visited his hometown in Syria.

'I liked what they are wearing, they were like one herd,' he said. 'They had a lot of weapons. So I spoke to them, and decided to go their training camp in Kafr Hamra in Aleppo.'

These children and the adults interviewed said there were youngsters aged 13 or younger undergoing the same training and performing the same military duties as adults.

Amr, 17, told Human Rights Watch that when he joined the jihadi movement full-time, he was given weapons and equipment, as well as a salary.

He even signed up for suicide missions because he felt social pressure to do so, although he was towards the end of the list, several hundred names down.

One doctor said he treated a boy aged between 10 and 12 years old whose job it was to whip ISIS prisoners.

In November last year, a United Nations Commission of Inquiry on Syria report found that massacres, the beheading of boys as young as 15, and amputations and lashings in public squares with residents - including children - forced to watch were on the list of crimes.

Propaganda: An Islamic State fighter carrying a flag poses with two young children in Benghazi, Libya

Young jihadi: Abu Bakr al-Faransi is believed to be the youngest French child to die fighting for ISIS in Syria

This disgusting Islamic State photograph shows a man forcing a tiny baby to kick a severed head

The research, based on interviews and documents, photographs and video footage released by the group itself, showed there was widespread use of child soldiers, and forcing women to bear children to the fighters.

This is about the brainwashing and sexual grooming of our young children. They have been preyed upon by sadistic fanatics Anthony Glees, director of the Centre for Security and Intelligence Studies

It also discovered children are subjected to violence and are systematically recruited as soldiers - forced to witness and carry out atrocities.

The report found ISIS was trying to indoctrinate minority children and turn them against their families.

Speaking to MailOnline, Professor Anthony Glees, director of the Centre for Security and Intelligence Studies at the University of Buckingham, said he wouldn't be surprised if hundreds of children had been recruited.

‘This is about the brainwashing and sexual grooming of our young children,' he said.

'It's very different from what happens when 18+ year olds become radicalised and are recruited into becoming jihadists. They are grown-ups and responsible for what they do.

‘They have been preyed upon by sadistic fanatics.'

Speaking to MailOnline, Professor Anthony Glees, director of the Centre for Security and Intelligence Studies at the University of Buckingham, said children have been 'preyed upon by sadistic fanatics'

An ISIS interviewer asks one child, who is standing alongside an armed companion, what his life is like under the Islamic State caliphate at a fairground north of Mosul in Iraq

He added: 'The prime responsibility for this lies with the radicalisers and recruiters and the internet service providers who provide the links that they follow with such dedication that they turn their backs on their loved ones and the good things that all children should have, whatever their faith or ethnic background.

‘Instead, they have been delivered to those who peddle exploitation and death. We here now have some very tough questions to address.

‘Our laws make it plain that we owe a very clear duty of care to the children. They are kids.’

Just yesterday, it was reported a 13-year-old from France had died fighting for Islamic State in Syria.

It's been reported that Abu Bakr al-Faransi, originally from Strasbourg, was killed when Government forces attacked a border post he was guarding. It is believed to be the youngest to die fighting for Islamic State in Syria.

And last month, it was revealed ISIS had released a guidebook to help young mothers raise a 'Mujahid child'.

'Don't wait until they are seven to start, for it may be too late by then,' it says.

Human Rights Watch has called on ISIS to stop deliberately recruiting children, in particular through weapons training and other military training in school environments.

Forced fashion: Some children have been dressed in ISIS-branded military uniforms and t-shirts