Beaming at the camera with an angelic smile, this little boy is at first glance a picture of innocence.

But though he is only six years old, and lives in the heart of British suburbia, he and his siblings are being groomed to support barbaric Islamic State terrorists.

In exclusive pictures obtained by The Mail on Sunday, the children are shown posing in front of the jihadis’ ‘black flag of Islam’ and brandishing a sword.

Terrible footage has already emerged of young children groomed to support IS in Syria and Iraq – but this boy was photographed inside a terraced house in suburban Luton. He was posing at the behest of his father Ibrahim Anderson, one of Britain’s most infamous jihadi Muslim converts.

Shocking images of children were taken from the mobile phone of Ibrahim Anderson, a red-haired convert, to Islam who was arrested for setting up a stall on Oxford Street, London, to persuade people to join ISIS. This boy is only six years old, and he and his siblings are being groomed to support barbaric Islamic State terrorists

In another picture, the boy’s older brother, eight, can be seen in a similar pose, brandishing a sword in front of the black flag, while wearing a Western T-shirt emblazoned with Kermit the Frog

The third photograph shows their toddler sister, said to be under three. Wearing a pink hijab despite her age, she smiles at the camera while perching on the back-rest of a sofa

Anderson was convicted at the Old Bailey on Friday of ‘inviting support for IS’ in the first successful case of its kind. Disturbingly, his son is holding a sword in his left hand, apparently ‘paying tribute’ to the late executioner Jihadi John, who cut the throats of his victims holding a hunting knife in the same hand. The boy also raises his right index finger, mimicking a gesture jihadis use to signify their one God.

In another picture, the boy’s older brother, eight, can be seen in a similar pose, brandishing a sword in front of the black flag, while wearing a Western T-shirt emblazoned with Kermit the Frog. The third photograph shows their toddler sister, said to be under three. Wearing a pink hijab despite her age, she smiles at the camera while perching on the back-rest of a sofa.

The black flag of Islam contains the Arabic words: ‘There is no god but Allah, and Mohammed is the Messenger of Allah.’ But it has been appropriated by extremist groups. In the UK, it was routinely used in demonstrations by Al-Muhajiroun, the banned group which wanted to raise it above 10 Downing Street. These pictures were taken on Anderson’s mobile phone in October 2014 and were discovered by detectives when they raided his home two months later. They were shown to the jury at his trial.

Born Andrew Anderson, he converted to Islam while serving three years in jail for a petrol station robbery in the late 1990s. He had previously been jailed for car theft. Before his arrest he was living with his wife, the mother of the children, in the Bury Park area of Luton. She too is a British convert and grew up in Nottingham.

The children's red-bearded father Ibrahim Anderson talks to members of the public in suburban Luton

Before his arrest, Anderson was living with his wife, the mother of the children, in the Bury Park area of Luton. File picture

During the landmark court case, the jury was told that Anderson, 38, and his co-accused, Shah Jahan Khan, 63, set up a stall in Oxford Street, Central London, to recruit for IS. They were only brought to justice after a concerned Muslim passer-by contacted police.

The court heard the two extremists spent two hours in August 2014 handing out leaflets promoting IS.

Anderson belongs to the same group of London extremists who have urged followers to ‘behead’ anyone who draws images of the Prophet Mohammed and formed vigilante ‘sharia patrols’ to harass gay people

Officers also found disturbing pictures on Khan’s mobile phone. Four young children – believed to be members of his family – were pictured in front of a sign reading ‘Khilafah est 2014’ – an apparent reference to IS setting up their caliphate in Syria and Iraq in 2014.

Anderson belongs to the same group of London extremists who have urged followers to ‘behead’ anyone who draws images of the Prophet Mohammed and formed vigilante ‘sharia patrols’ to harass gay people and tried to stop public drinking in East London. Other members of this group have included Michael Adebolajo and Michael Adebowale, who killed drummer Lee Rigby outside his barracks in Woolwich, South-East London, and Siddharta Dhar, the new IS executioner replacing Jihadi John.

Anderson was previously charged but cleared of heckling a homecoming parade by the Royal Anglian Regiment in Luton in 2009. The convert, who also has a boy of 13, even posted one photo of his children on Facebook, but it was taken down for violating rules on hate messages.

Last night Anderson’s 58-year-old stepfather, Martin Warner, told this newspaper that the ‘sick’ extremist had ‘always been a problem child’, adding that the family had disowned him after his conversion to radical Islam. He added: ‘I can’t believe he made his children pose with the IS flag – it is disgusting. He is a total idiot, a fanatic. He is the sort of person who would blow himself up or plant a bomb. He is dangerous. They should throw him in prison and throw away the key.’ Anderson and Khan will be sentenced on Friday.

Tory MP Philip Hollobone said: ‘Not only is this child grooming, this is child abuse. We can’t have children being brought up in this country to become potential suicide bombers, groomed by their own parents. These children should be taken into care, if appropriate.’

Labour MP Keith Vaz said: ‘These images are disturbing and demonstrate the extent to which people are prepared to go in support of IS.’

Extremists grooming their children has become a huge concern. Sources estimate that up to 100 British children under 16 are in IS-controlled Syria and Iraq. In Britain, more than 20 children have been made the subject of court orders amid fears they could be radicalised.