The brother of two British teenagers killed fighting for Islamists in Syria has died in hospital after being stabbed in a car after it crashed.

Abdul Deghayes, from Brighton, died in the early hours of Sunday morning in the East Sussex city, Sussex Police confirmed as they announced they had launched a murder investigation.

The 22-year-old was found just before 9.30pm on Saturday in the passenger seat of a silver Volkswagen Polo which had crashed into other cars, police said.

He had a "number of stab wounds" and died from his injuries at the Royal Sussex Country Hospital, a spokesman said. Elm Grove, where the incident took place, remains cordoned off.

Chief Inspector Andy Bennett appealed for witnesses to come forward and said: "We are trying to establish the exact circumstances of what has led to this young man's tragic death.

Abdullah Deghayes was killed fighting in Syria credit: Facebook

"We are aware the car was in collision with other vehicles shortly before he was found to have suffered these injuries, which we are satisfied were caused maliciously and not as a result of the collision."

Abdul - who was jailed in 2017 for drug dealing - is the twin brother of Abdullah who was killed fighting in Syria in 2016 aged 18.

Their younger brother Jaffar, 17, was killed in 2014 while trying to overthrow Bashar Al-Assad's government.

Speaking at the time of Jaffar's death their father Abubaker Deghayes said his grief "cannot be described" as he claimed the Government was "criminalising" young Britons who have travelled to the war-torn country.

Jaffar Deghayes, 16, brother of Abdullah Deghayes who was killed in Syria

A serious case review published in 2017 found professionals missed opportunities to prevent the two teenage British Muslims being radicalised before they were killed after travelling to fight in Syria.

There was "no recognition" that Abdullah, Jaffar and their three siblings were becoming vulnerable to radicalisation in Brighton, the report said.

There was also little understanding of the part religion played in the lives of Abdullah and Jaffar, who were believed to have been with the al Qaida-affiliated Al-Nusra Front when they died, the review added.

A third brother, Amer Deghayes, a former finance student, also travelled to Syria in a bid to overthrow dictator Bashar Assad's government.