West Yorkshire Police identified the three as Khadija Dawood, Sugra Dawood and Zohra Dawood and said they were "extremely concerned for the safety of the family".

The three women and the youngsters had gone on an Islamic pilgrimage to Saudi Arabia.

But the nine failed to return to the UK four days ago and worried relatives contacted the police.

It has emerged the family had flown on 9 June from Medina in Saudi Arabia to Istanbul in Turkey - a commonly used route into Syria.

It is feared the nine, from Bradford, may have then gone to Syria to join a relative believed to be fighting for extremists there.

Sky's Mark White said: "The family took a flight from Saudi Arabia to Istanbul but then appeared to have disappeared completely off the grid. Their mobile phones have been switched off."

Khadija Dawood, 30, Sugra Dawood, 34, and Zohra Dawood, 33, left Britain on 28 May for Saudi Arabia, said Balaal Khan, a lawyer acting for the fathers of the missing children.

Among the youngsters are Khadija Dawood's children Maryam Siddiqui, seven, and five year-old Muhammad Haseeb.

Sugra Dawood's children Junaid Ahmed Iqbal, 15, Ibrahim Iqbal, 14, Zaynab Iqbal, eight, Mariya Iqbal, five and Ismaeel Iqbal, three, have also disappeared.

As have Zohra Dawood's children Haafiyah Binte Zubair, eight, and five-year-old Nurah Binte Zubair.

Mr Khan said: "They (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."

He said the sisters and their children have not been in contact for nearly a week, and their Facebook profiles have not been updated.

Mr Khan said: "It started with a pilgrimage to Saudi Arabia and they were meant to return on June 11, however they have failed to return.

"It has been revealed that on 9 June they have travelled from Medina to Istanbul. Since that day their family have not had any contact with them and their Facebook and 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."

He said police were notified five or six days ago, but are limited in what they can do because it is out of the jurisdiction.

A West Yorkshire Police spokeswoman confirmed they have received a missing persons report concerning the Dawood family.

The force said that since their disappearance was reported it has been supporting the family.

It added that officers have started an investigation to establish their whereabouts and are "working extensively with authorities overseas to try and locate them".

Assistant Chief Constable Russ Foster, of West Yorkshire Police, 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."