A third British jihadist from Portsmouth has been reported killed fighting in Syria, according to religious authorities in the city.

Manunur Roshid, 24, was known to be one of a group of six men from Portsmouth who went to Syria in 2013. Reports of his death follows that of Ifthekar Jaman, 23, last December and Muhammad Hamidur Rahman, 25.

Experts in tracking the movements of foreign fighters in war-torn Syria said Roshid may have been killed in the battle of Kobani, where Isis (Islamic State) is fighting Kurds backed with US air strikes for control of the town, which borders Turkey.

The chair of Portmouth’s Jami mosque, Abdul Jalil, told the Portsmouth News that Muslim residents were shocked to hear of another young man’s death and that there also had been reports that a fourth man from the city had been hospitalised in Syria.

“We are very worried. They are on the front line,’ Jalil said. “It is a very big shock for their parents and we are working with the community to make sure that [something like this] does not happen again.”

“We are working with the police, the crime prevention team and the council to warn people, our youngsters especially, telling them not to go to Syria and also to get parents to watch their children,” he added.

The newspaper reported that Roshid was killed on Friday and that his family learned of his death on Sunday.

Shiraz Maher, a senior researcher at King’s College’s International Centre for the Study of Radicalism, said: “It is probable that Roshid died in the battle for Kobani as another of his Portsmouth counterparts, Muhammad Mehdi Hasan, is known to be fighting there, although we haven’t been able to independently verify this yet.”

Maher said the centre had so far confirmed the deaths of 25 jihadists who travelled from Britain to partake in the Syrian civil war.

“The Portsmouth cluster of fighters is perhaps one of the best known. In total, six men went to join Islamic State last year. Now three are dead, one returned to the UK and is in jail, and two remain fighting in Syria.”