Pictured smiling happily at the airport, these are the last photographs taken of the missing children among a family of 12 who are feared to have fled to Syria to join Islamic State.

The missing dozen, made up of three sisters and their nine children, are believed to have travelled to the war-torn country, despite being under extensive police surveillance.

The family – who include children aged between three and 15 – were originally thought to have gone on a pilgrimage to Saudi Arabia.

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This picture appears to show some of the Dawood family at the airport leaving the UK for Saudi Arabia. Pictured are Junaid Ahmed Iqbal, Ibrahim Iqbal, Zaynab Iqbal, Ismaeel Iqbal and Mariya Iqbal

Sisters Sugra Dawood 34, Zohra Dawood, 33, and Khadija Dawood, 30, travelled to Saudi Arabia for a pilgrimage with their nine children, including (from left) Zaynab Iqbal, Ismaeel Iqbal and Mariya Iqbal

But police believe they may have followed in the footsteps of their brother, who travelled to Syria to fight for ISIS two years ago.

The sisters had been expected to return home to Bradford last Thursday but officers believe they instead boarded flights to Istanbul in Turkey two days earlier.

Sugra Dawood is thought to have fled with her five children – Junaid, 15, Ibrahim 14, Zaynab, eight, Mariya, five, and three-year-old Ismaeel.

They were understood to be with 33-year-old Zohra Dawood and her children – eight-year-old Haafiyah and five-year-old Nurah – and 30-year-old Khadija Dawood with children Muhammad, five, and seven-year-old Maryam.

If the family's fears are confirmed, they would be the largest family to have travelled to join ISIS from the UK if they have fled to Syria.

Last night a family friend revealed the sisters had been under surveillance for a ‘long period’ after their brother went to Syria around two years ago.

The friend said: ‘The girls and the whole family knew they were being watched by the police and security services. It was an open secret.

‘Their brother went to fight in Syria about a couple of years back. Knowing they were being watched so closely may have helped them make their decision to leave for good.’

From left, clockwise, Junaid Ahmed Iqbal, Ibrahim Iqbal, Ismaeel Iqbal and Zaynab Iqbal are missing

Ismaeel Iqbal and Mariya Iqbal are pictured with suitcases behind them. They appear to be at the airport

Balaal Khan, a lawyer acting for the fathers of the missing children, said yesterday that the sisters left the UK on May 28 to go on an Islamic pilgrimage to Saudi Arabia.

They were supposed to return on June 11 but boarded a flight from Medina in Saudi Arabia to Istanbul – a route used by many entering Syria to join the extremists.

Last night Mr Khan said: ‘[The fathers] are concerned that their children’s lives are in danger. The concern is for the well-being and safety of the children.

‘The fathers are distraught, they feel helpless and they don’t know what to do. They want the children out of harm’s way.’

The lawyer added that the sisters and their children have not been in contact for almost a week.

Sisters Zohra Dawood, 33, (left) and Khadija Dawood, 30, (right) are feared to have fled to join Islamic State

Mother-of-five Sugra Dawood (left) also disappeared with her sons Junaid Ahmed Iqbal, 15, (left) Ibrahim Iqbal, 14

He said: ‘It has been revealed that on June 9 they have travelled from Medina to Istanbul. Since that day their family have not had any contact with them and their Facebook and [messaging service] WhatsApp profiles have not been updated.

‘One of the possibilities is they travelled to Turkey to travel to Syria. The suspicion, and main concern, is that the women have taken their children to Syria.’

Khadija was described as a ‘good woman’ by a former neighbour, who said she was ‘very surprised’ by the news as they had seemed like a normal family. Her husband Shohaib, she added, was a security guard at a cinema.

A resident on the street where the Dawood family used to live said the family were normal and quiet.

The man, who did not want to be named, said: 'The father used to own a few houses on the street. They were a big family and you never had any trouble from them. They were just nice and normal.

Sugra's other five children Zaynab Iqbal, aged eight, (left) Mariya Iqbal (centre), aged five, and three-year-old Ismaeel Iqbal are also missing

'I didn't really know any of them, but they were decent people. I think the oldest children went to decent schools. I'm just so shocked to hear the news. Three women and nine children - it's unbelievable.'

Mr Dawood was unavailable at his home in Bradford, although local resident Mohammed Khan, 35, said he was disabled and in ill health.

'He has his son and three daughters who would look after him and now they've gone. It's terrible,' he said.

'I knew the brother had gone away about a year or so. So now the daughters have gone too, he has no one.

'From what I've heard they're a nice, quiet family. They keep themselves to themselves. I just hope they are all safe and everything turns out all right, especially with the kids.'

Mother-of-two Zohra Dawood disappeared with her two young daughters five-year-old Nurah Binte Zubair (left) and Haafiyah Binte Zubair, who is aged eight (right)

Mother-of-two Khadija's children Muhammad Haseeb, aged five, (left) and seven-year-old Maryam Siddiqui (right) are missing

Since the group left the UK police in West Yorkshire have carried out ‘extensive’ inquiries and have been working with forces overseas in a bid to track and trace the family’s movements.

Last night West Yorkshire’s Assistant Chief Constable Russ Foster said: ‘We are extremely concerned for the safety of the family and would urge anyone with information to come forward and speak to us.

‘Our priority is for their safe return; their families are gravely worried about them and want them home. One of our primary concerns is the safety and welfare of the young children.’

The force refused to confirm or deny reports that the sisters had been known to police prior to leaving the country.

A Foreign Office spokeswoman said: 'We are in contact with West Yorkshire Police and Turkish authorities and our ready to provide consular assistance.'

Calls had already been mounting for more to be done to tackle radicalisation of teenagers online after 17-year-old Talha Asmal was reported to have become Britain's youngest ever suicide bomber.

Mr Khan is pictured being interviewed by reporters outside Khan Solicitors in Leeds this evening

Police are seen leaving Khan Solicitors. A family of 12 from Bradford, including nine children, are feared to have fled to join Islamic State after failing to return from a pilgrimage to Saudi Arabia

Talha, 17, is alleged to have fled his home in Dewsbury, West Yorkshire, in March, to join ISIS. He reportedly detonated a vehicle fitted with explosives while fighting for the group in Iraq.

His family said he had been exploited by extremists on the internet 'in a process of deliberate and calculated grooming'.

Unbeknown to them and completely against their will, they said he travelled to Iraq via Turkey and fell under the spell of ISIS handlers who are 'too cowardly to do their own dirty work'.

Shahid Malik, a former government minister and a family friend of the Asmals, said yesterday: 'This is a clear indication of just how successful the evil Isis groomers have been in poisoning and brainwashing Talha and kids like him.'

The former reviewer of anti-terrorism legislation, Lord Carlile, also called on the Government to work with computer programmers and social media companies to counter extremist propaganda online.

It came after three schoolgirls from Bethnal Green, East London, left the UK in February to join ISIS.

Shamima Begum, Amira Abase and Kadiza Sultana all disappeared from their homes and flew to Turkey, before crossing the border into Syria.

The family are believed to have boarded a fight from Medina in Saudi Arabia to Istanbul in Turkey

It is understood they were following another 15-year-old girl who had travelled there in December. As many as 600 people from the UK have travelled to join ISIS jihadis in Syria and Iraq, including many young women.

Separatelyl, a British couple left their Berkshire home with their four young children in April in a bid to escape to Syria but were later arrested in Turkey.

Asif Malik, 31, his partner Sara Kiran, 29, and their four children were caught on CCTV boarding a cross-Channel ferry from Dover. After arriving in Calais, they travelled south through Europe in a bid to flee to Syria.

However, Turkish officials told how the family group had been arrested in Ankara and were placed in custody with their four children – daughter Zoha, seven, and three sons Essa, four, Zakariva, two, and Yahya, one.

Yesterday Metropolitan Police Commissioner Sir Bernard Hogan-Howe, speaking before a counter-terrorism conference, said: ‘Today’s terrorist may of course be a hardened member of an organised terrorist “cell” – but may very well also be a lone disaffected youth radicalised by extremist material on his home computer.