Mohammed el-Araj, from west London, is only second Briton confirmed to have been killed fighting in conflict.
A British Muslim has been killed fighting against Bashar al-Assad's forces in Syria, his family in London have said.
Mohammed el-Araj, who was in his early twenties, is only the second Briton to have been named and confirmed as dead while fighting in the civil war. Araj, who spent 18 months in prison for violently protesting outside the Israeli embassy in London in 2009, was killed in Syria in mid-August.
The International Centre for the Study of Radicalisation (ICSR), a thinktank that has been tracking hundreds of foreign fighters going into Syria, said that news of his death had been associated with propaganda from two major al-Qaida-linked groups, including video and postings on web forums.