Merah killed seven people in Toulouse in shooting spree three years ago

Adult jihadist in ISIS video is believed to be French citizen Sabri Essid

The film never shows the boy's face in the moments leading to his death

But there are clues which raise doubts over whether he pulled the trigger

In edited video, a young boy, appears to shoot the hostage at close range

The father of an Israeli-Arab man who is said to have been shot dead by a child in the latest video from Islamic State militants claims his son was tricked into joining the terror group.

Speaking today from his home in Jerusalem, Said Musalam said jihadists lured his 19-year-old son Muhammad to Syria with promises of women, money and cars.

He added that the teenager was captured and killed when he tried to return home when he learned his mother was sick.

It comes one day after ISIS released a video purporting to show a boy, who appears to be no older than 10, carrying out the execution of Muhammad with a gunshot to his forehead.

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Speaking from his home in Jerusalem, Said Musallam said jihadists lured his 19-year-old son Muhammad with promises of women, money and cars. Above, Said Musallam with his wife and a photo of Muhammad

Final moments: Muhammad Said Ismail Musallam, who the Islamic State claim was working for Israeli intelligence when he was captured in Syria last year, is seen kneeling in front of ISIS militants in the video

Serious questions have been raised over the authenticity of the video after careful editing never actually implicates the child shown in the clip as having killed the prisoner

But heavy editing used to produce the film means it is likely he never pulled the trigger himself and was instead filmed only for scenes to be edited in and around Mr Musallam's death.

The terrorists claimed Mr Musallam had been working as a spy for Israeli intelligence forces - an accusation denied by his father.

Said Musallam said his son had tried to come home from Raqqa, the group's de-facto capital, after learning that his mother was sick but was killed when he tried to flee.

'They did not want to let him leave because if he comes back, he might be caught by the Israelis and tell them what he had seen. So they wanted to get rid of him,' he said.

'I know my son. I raised him well. I am sure he's not working for the Mossad.'

The film shows Mr Musallam describing how he was sent by Israeli intelligence to infiltrate ISIS in Syria, where the group claim he was captured last year.

Wearing an orange jumpsuit, the hostage is later seen kneeling at the feet of two uniformed militants.

The film, like many ISIS execution videos, cuts away without actually showing his killing, and the scene purporting to show the moment of execution is filmed from behind the shooter to avoid identifying him.

During this scene, the shooter's hand is visible and it clearly appears to be one which belongs to an adult, not a 10-year-old boy.

Brutal: While ISIS claim the child - described in the video as one of the 'cubs of the caliphate' - was the shooter, this frame purporting to show Mr Musallam's shooting clearly features a man's hand on the trigger

It also replicates the editing techniques seen in a video released last month in which the extremists claimed a boy had killed two Russian spies.

Speaking today, Said Musallam said he as the only one in the family to watch the video.

He said he saw his son dressed in orange, knew that he was marked for death, and could not watch it through to the end.

His wife cried and she and other family members were too distraught to watch, he added.

The family said it had begun a customary three-day mourning period, though there will not be a mourning tent because they live in a Jewish area of east Jerusalem.

He added that he wished the same fate upon the family of Islamic State group's leader Abu Bakr al-Baghdadi.

'I will leave it to God and what happened to my son Mohamed I hope God will do the same for you, your sons and your family,' Musallam said in Arabic, addressing al-Baghdadi.

'God knows that one day we'll meet, whether in paradise or in hell, and we'll settle the accounts.'

It came after reports the adult jihadist who appeared in the video is the step-brother of a French Muslim who murdered seven people in a killing spree in France three years ago.

The ISIS extremist was named by French anti-terror experts as French citizen Sabri Essid.

Sickening: Mr Musallam appears to be shot three more times as he lies dying on the ground

His father married the mother of Mohamed Merah, who gunned down a rabbi and three children at a Jewish school in Toulouse and killed three others before dying in a hail of gunfire in March 2012.

Voice analysts said the man thought to be Essid also spoke in a pronounced Toulouse accent similar to that of Merah and his family.

The ISIS militant also refers to attacks in France and vows that Islamic State will murder Israelis and 'conquer Jerusalem'.

Essid left France for Syria in 2014 as did Souad Merah, the sister of the Toulouse gunman.

The boy was also identified as French.

French government spokesman Stephane Le Foll described the video as a 'dreadful' killing, but refused to comment Wednesday on the nationalities or identities of the man and boy.

The authenticity of the video - and the child's role as gunman - can be seriously questioned given a complete lack of evidence implicating the child.

However, the Florida-based Terrorism Research & Analysis Consortium (TRAC) said that the video did look genuine. TRAC's Veryan Khan said it appears the boy had quite a few 'dry runs' before the actual execution because he seemed 'well trained.'

She added: 'Notice how he takes his finger off the trigger after firing and rests it to the side of the trigger? He wasn't red in the face and wasn't even shaking. This indicates proficiency with a pistol, only people who are trained know to rest their finger to the side.'

She also pointed out that the production team were the same which put together an ISIS video of a child executing other 'spies' that was released in January.

Earlier yesterday Twitter accounts linked to the terror group shared preview clips of the video, which have not been independently verified.

The young boy, who appears to be no older than 10, leads Mr Musallam into the field, but it is likely the child never actually pulled the trigger himself

Islamic State claimed Mr Musallam had posed as a foreign fighter when he joined their ranks last year but later confessed to being an agent for Mossad, the Israeli intelligence agency.

The accusation has been denied by an Israeli security official and by his parents - who claimed he had travelled to the region to fight alongside the jihadists.

The video, published today by the group's Furqan media outlet, is the latest in a series of propaganda videos that purportedly show the execution of ISIS hostages, including three Britons.

It also lists the names of 13 other men - including Mr Musallam's elder brother and father - who the group claims are working for Mossad.

Featuring graphics, re-enactments and a number of camera angles, the film includes a number of camera effects and cut-away shots that give it a 'computer game' look.

It starts with an animated 'fact file' of Mr Musallam - complete with what appears to be a picture of the inside of his passport - that claims to show his home address and profession.

The video, apparently filmed on a number of cameras, shows Mr Musallam wearing an orange jumpsuit similar to those worn by hostages featured in previous ISIS videos.

Speaking in Arabic, the young man remains calm and controlled as he tells of how he was recruited by a neighbour who worked for the Israeli police. The entire video is subtitled in English.

He says that his father and brother both encouraged him to take up the position, pointing out there would be opportunity to progress in the organisation.

Harrowing: The footage shows the 19-year-old prisoner just moments before he is shot in the head, pictured

Slick: In the first part of the video, Mr Musallam is seen describing how he was recruited by Israeli intelligence

He adds: 'I knew at that point they themselves were working as spies'.

Mr Musallam goes on to describe how he was trained to use weapons and withstand interrogation techniques at a camp in Jerusalem before being sent to Syria on a mission.

He explains he was told to infiltrate the Islamic State and send information on weapon stores, training bases and Palestinian members of the group back to Israel.

In what appears to be a rehearsed speech, Mr Musallam talks about how he entered Turkey before being smuggled across the border to Islamic State-occupied Syria.

He shares of how he was caught and interrogated by jihadists after they became suspicious when he left a guest house where he was staying to make a phone call to his father.

It was during the interrogation that he confessed to being an Israeli spy, he claims.

Mr Musallam then urges his father and brother, whom he blames for 'getting him in this mess', to 'repent' for what they have done.

He adds: 'I say to those who come to the Islamic State, you won't succeed at all.'

The first part of the video ends with the words 'to be executed' being branded across Mr Musallam's face before fading to black - just one of a number of effects used in the film.

He is then seen being led into a field by a young boy, who appears to be no older than 10.

Dramatic music starts playing as the camera reveals Mr Musallam, kneeling in a field.

Behind him, the adult ISIS militant, dressed in the same camouflage uniform as the boy, begins speaking in French, calling on 'Jewish spies' and their recruiters to be killed.

A tweet from the anti-ISIS campaign group (pictured) stated his execution would be broadcast in the near future, after he was interviewed in the latest edition of the terror group's online magazine

He says: 'Allah granted us the grace to murder Jews on their lands in France.'

'As to what happens here in the Islamic State, these are our young lions. They will kill those sent by the stupid Mossad to spy on the secrets of the Mujahedeen and the Muslims.'

The man then pushes the young boy forward - directing him to stand in front of Mr Musallam.

The child raises his gun, aiming it at the hostage's forehead before it suggests he shoots him at point-blank range.

However, it is impossible to tell whether it is in fact the child who is shooting as the camera cuts to show just a hand - which may even belong to an adult - on the trigger.

Mr Musallam appears to be shot a further three times as he lies on the ground.

This image was purportedly taken of Muhammad Musallam on the Syrian-Turkish border several weeks after he left to join jihadists

The purported child executioner lifts his gun to the sky in celebration, shouting 'Allahu Akbar!' before appearing to fire one final shot.

The video ends with a list of 13 men - including Mr Musallam's brother and father - who ISIS claim are acting as Mossad agents.

Each name is accompanied by text that claims to list the individual's home address and occupation.

The release of the brutal video comes after an interview with Mr Musallam was published in the latest edition of Islamic State's online English-language magazine last month.

In it, he said he had joined the insurgent group in Syria so as to report to the Israelis on its weapons caches, bases and Palestinian recruits.

After his conduct aroused the suspicion of Islamic State commanders, Mr Musallam was quoted as saying, he broke cover by phoning his father in East Jerusalem, leading to his capture.

'I say to all those who want to spy on the Islamic State, don't think that you're so smart and that you can deceive the Islamic State. You won't succeed at all,' he said, according to Dabiq.

'Stay away from this path. Stay away from helping the Jews and the murtaddin (apostates). Follow the right path.'

According to Haaretz, Mr Musallam's father, Said, denied his son was a spy, saying he went missing after visiting Syria to join ISIS.

The paper reported his father as saying: 'He is not a spy, he went over on his own - they recruited him on the internet.

'I don't know what they said to him or how they got into his head, but he is not connected with the Mossad, the Shin Bet security services or anyone else.'

An Israeli security official said Mr Musallam traveled to Turkey on October 24 in order to fight for Islamic State in Syria.

'He went on his own initiative, without his family's knowledge,' the official said.

Worried that members of its 20 per cent Arab minority might travel to Syria or Iraq to join Islamist insurgent groups and then return radicalised and battle-ready, Israel has stepped up monitoring and prosecution of suspected would-be volunteers.

Turkey draws many Israeli Arab holidaymakers. It is also a major conduit for foreigners who slip across the border to help insurgents trying to topple Syrian President Bashar al-Assad.