A video appearing to show British members of the Islamist group Isis has appeared online.
In the video, which has not yet been verified, one of the group says they will take their fight to Jordan and Lebanon, as well as Iraq, where they say they are travelling to.
The speaker, identified as "Brother Muthanna al-Yemeni from Britain" also says that the force includes fighters from countries including Bangladesh, Cambodia, Australia and the UK.
Although there are no definite numbers on how many Britons are fighting with Isis, the authorities have estimated there are about 400 in total.
Kurdish counter-intelligence have said there are 450 Britons in Iraq alone, although that figure is highly disputed.
ITV News diplomatic correspondent John Ray says the fact the group are not trying to hide their identities "would suggest that if they are out in Syria and Iraq, they're not intending to come home".
Leaders of a Cardiff mosque, attended by 3 young men who are now fighting in Syria, say they had nothing to do with their radicalisation.
The Home Secretary has told ITV News that young women have left Britain to fight for the extremists group ISIS in Syria and Iraq.