London school girls
Shamima Begum, 15, Amira Abase, 15, and Kadiza Sultana, 16, left on a flight to Turkey on 17 February. Met Police

A 15-year-old London girl who preceded the three schoolgirls who travelled to Syria to join Islamic State (Isis) has been named as Sharmeena Begum.

Begum fled her Bethnal Green home for the civil war torn country in December, her father Mohammad Uddin told the Daily Mail.

Two months later she was followed by her best friends: Kadiza Sultana, 16, Amira Abase, 15, and Shamima Begum, 15. Shamima Begum is not thought to be related to Sharmeena Begum.

Uddin said his daughter enjoyed shopping, watching EastEnders and listening to Rihanna up to her mother's death 18 months ago.

"Before then she wasn't very religious. She wouldn't go to the mosque and she would wear English dress," he told the paper. "But then she changed her dressing style and wore a scarf and started praying five times a day.

"Sometimes she would go to the East London Mosque for prayers."

Uddin said he believed she was groomed by Islamist radicals online. "I think the police should monitor the internet more because it's destroying lives. It's not fair," he said.

Sharmeena boarded a flight from London to Istanbul in December, before crossing the Turkish border into Syria, without her father's knowledge.

Two weeks later she called her father to say she was in IS-held territory. "I'm in Islamic State and I'm not coming back," Uddin claims she said.

Uddin said he warned police and his daughter's school to monitor her three friends.

Sultana, Abase and Begum completed a similar journey, flying from Gatwick Airport to Istanbul on 17 February.

They then took a bus from the Turkish capital to the southern city of Gaziantep, a notorious entry point for foreign fighters travelling to Syria. From there they were smuggled across the border by a man, who Turkish authorities claim was a double agent for a foreign country.

A video purportedly showing the alleged spy helping the three schoolgirls pass their baggage from a taxi to the vehicle that would take them from Gaziantep to Syria was published by Turkish media this week.

Turkey's foreign minister Mevlüt Çavuşoğlu announced the man – an alledged – smuggler was arrested earlier this week.

Begum and her three friends and are now believed to be living in the IS stronghold Raqqa.