A British woman who travelled from east London to join Isis and was later linked to the radicalisation of Shamima Begum has been arrested in Syria, according to reports.

Sharmeena Begum, 27, is understood to have been detained after investigators examining a deadly attack at Berlin Pride earlier this year traced communications between her and the suspected attacker.

German authorities are understood to have uncovered messages exchanged between Begum and Abdul Ballout, who allegedly carried out the attack in July, The Mail on Sunday reports.

According to reports, Ballout sent Begum a video pledging allegiance to Isis before launching the assault. He later drove a van into crowds attending Pride celebrations before attacking people with a machete, killing one woman and injuring dozens more.

He was subsequently shot dead by police following a manhunt.

German investigators passed Begum's phone number to a Western intelligence agency, which allegedly tracked her to a hideout in Syria, leading to her arrest.

Begum, who left the UK in December 2014 while still a teenager, became one of the earliest British schoolgirls to travel to territory controlled by Isis. She attended Bethnal Green Academy in Tower Hamlets and has long been associated with the radicalisation of fellow pupils, including Shamima Begum, who travelled to Syria in February 2015 alongside friends Amira Abase and Kadiza Sultana.

While Shamima Begum has publicly distanced herself from the terror group since the collapse of the so-called caliphate, Sharmeena Begum was reported to have remained supportive of Isis ideology.

Reports have previously suggested she criticised her former schoolmate and continued to express sympathy for the organisation years after its territorial defeat.

Her father, Mohammed Nizam Uddin, told the newspaper he had believed his daughter had been killed in Syria and had not been informed of her reported detention.

Following the fall of Isis, thousands of women and children linked to the group were held in camps run by Kurdish authorities in northern Syria. Begum is reported to have escaped from one of those facilities before later raising money online that investigators believe was intended to assist Isis-linked women and children.

She is expected to face terrorism-related proceedings in Syria. Reports suggest she was stripped of her British citizenship several years ago, meaning the UK Government has no obligation to assist her.

The reported arrest means all four of the Bethnal Green Academy schoolgirls who travelled to join Isis have now been accounted for.

Kadiza Sultana and Amira Abase are believed to have died in Syria, while Shamima Begum remains in a detention camp and continues to pursue legal efforts to challenge the removal of her British citizenship.