A teenage jihadist from Portsmouth has become the fourth extremist from the city to be killed fighting with Isis in Syria.

Mehdi Hassan, 19, travelled to the war-torn country in October last year with a group of friends calling themselves the “Britani Brigade Bangladeshi Bad Boys”.

Photos purporting to show his dead body appeared on Isis-affiliated Twitter accounts on Friday night, with fellow militants claiming he was killed fighting in Kobani.

The Syrian border town has seen intense fighting in recent weeks, with the US-led coalition bombing Isis militants and dropping weapons to Kurdish fighters attempting to stop the group’s advance.

The Foreign Office said it could not confirm Mr Hassan’s death but “was aware of reports about the death of a British national in Syria”.

Mehdi Hassan's Twitter account (Twitter)

The news did not reach his family, who live in Southsea, until Saturday morning as gruesome pictures of his body circulated on social media.

The chairman of their local Portsmouth Jami Mosque, Abdul Jalil, said he had spoken to Mr Hassan’s relatives.

“It has been confirmed with the family that he has died. Right now they are very upset,” he told the BBC.

“I am saddened and again shocked for the community about this news.”

The teenager, a former pupil at the independent St John’s College in Southsea, flew to Turkey and crossed into Syria instead of going to university.

His friends, Iftekar Jaman, Mamunur Roshid and Hamidur Rahman, have previously been killed in the fighting.

Mr Roshid’s death, at the age of 24, had been confirmed on Tuesday.

People watch an explosion after an apparent US-led coalition air strike on Kobani, Syria (EPA)

Mr Hassan went by the name Abu Dujana in Syria and on social media.

He last posted on his Twitter account @AbuDujana___ on 17 October, writing about the intensity of air strikes in Ayn al-Arab – an alternative name for Kobani.

“Between 20-40 us strikes daily in ayn al arab. Alhamdulillah they are spending $10's of billions...against themselves,” he wrote.

He had previously written about jihad and the goal of “ultimate success in the hereafter”, although his account had been deleted by Twitter several times.

Mashudur Choudhury, who left the UK with Mr Hassan, returned to the UK after just a few weeks and was arrested at Gatwick Airport.

He has since been convicted of terrorist offences in the first such case related to the conflict in Syria.

Assad Uzzaman is believed to be the last surviving member of the “Bad Boys” still fighting there.

An estimated 500 Britons are among 2,000 foreign fighters who have joined Isis, which calls itself the Islamic State.