CCTV footage has emerged of three teenage girls who are believed to have fled to Syria to join Islamic State.

Shamima Begum, 15, Kadiza Sultana, 16, and 15-year-old Amira Abase are caught on the video, standing at a bus station in Istanbul.

The video was recorded on Feb. 17, the day the three friends left their homes in East London after telling their families they would be out for the day.

It is believed the teenagers boarded a flight to Turkey from Gatwick, and have since crossed the Turkish border into Syria. Shamima was able to travel to Turkey using her 17-year-old sister's passport. It is feared they have been recruited by jihadists who groomed them online.

The girls' families have made emotional pleas for them to return home.

Amira's father, Abase Hussen, clutched a teddy bear wearing a Chelsea FC T-shirt. He said Amira had bought the teddy as a present for her mother. "The message I have for Amira is to get back home, we miss you, we cannot stop crying. Please think twice," he said.

They were students at Bethnal Green Academy in east London. Earlier this week the school said there was "no evidence" that they were at risk from radicalization. The three girls were friends with a fourth teenage girl from the same school who police believe is already in Syria, having traveled to Turkey in December 2014.

Met Police were forced to defend accusations they took too long to act after being alerted about the missing teenager's plans to travel to Syria. Shadow Home Secretary Yvette Cooper added the airline has "serious questions" to answer about how it allowed the three girls to travel unaccompanied.

As many as 500 Britons are thought to have made their way to Syria or Iraq to join Islamist groups. Around half have since returned, and dozens have been arrested in Britain under anti-terrorism legislation.

Anyone with any information on the girls' whereabouts should call the freephone Anti-Terrorist Hotline number on 0800 789 321.