A video has emerged showing three British men urging UK Muslims to join insurgents in Syria and Iraq.
In the 13-minute video, entitled There is No Life Without Jihad, the men announce that they are preparing to travel to Iraq to fight there.
One of the men in the film, propaganda for the extremist militant group Islamic State in Iraq and Syria (Isis), is a 20-year-old aspiring medical student from Cardiff.
Nasser Muthana, who goes by the name Abu Muthanna al-Yemeni, travelled to Syria with his 17-year-old brother Aseel Muthana after disappearing in November.
His father, Ahmed Muthana, said his elder son had been accepted at four universities to study medicine but did not go. Instead he thinks Muthana, who went to Cathays High School, gained 11 GCSEs and enjoyed swimming and football, became “brainwashed” and radicalised in the UK, he told the Daily Telegraph.
Mr Muthana is one of three men apparent Britons who appear in the video, which calls for their countrymen to “answer the call and fight for Allah”.
In the footage, Mr Muthana claims that the rebel group has fighters from as far afield as Cambodia, Australia and the UK.
“We are a state who is implementing the Sharia in both Iraq and the Sham. And look at the soldiers, we understand no borders,” he says.
“We have participated in battles in Sham and we will go to Iraq in a few days and we will fight there.
"We will even go to Lebanon and Jordan with no problems, wherever our Sheikh (Isis leader Abu Bakr al-Baghdadi) wants to send us."
A second British fighter in the video, who goes by the name Abu Bara’ al-Hindi, asks: “Are you willing to sacrifice the fat job you’ve got, the big car you’ve got, the family you’ve got? Are you willing to sacrifice this for the sake of Allah?”
He adds: “My brothers, living in the West, I know how you feel. When I used to live there I used to feel depressed. You feel like you have no honour. Come to jihad, feel the honour we are feeling.”
The government is treating the growing threat from Isis with ever-greater seriousness.
On Thursday the terror group was added to a list of banned organisations, making it an offence to be a member. Four other Syria-linked terror groups were banned at the same time.
British prime minister David Cameron has insisted "everything that can be done is being done" to stop Britons being radicalised overseas amid fears that 450 people have joined the ranks of the extremist group in Iraq.
The BBC reported that the Security Service, MI5, has made tracking British jihadists fighting in Syria its top priority.
Experts believe the method of appeal in the video mimicks that of Western charities and aid groups.
Joseph Carter, from the International Centre for the Study of Radicalisation at King’s College London, said: “There’s no question that the purpose is to attract Western audiences and to convince them to come.
“Unlike other groups who put out attack videos or feature major leaders, Isis feature everyday soldiers, people’s personal narratives.”
The Home Office said: “We do not tolerate the existence of online terrorist and extremist propaganda, which directly influences people who are vulnerable to radicalisation.
“We already work closely with the internet industry to remove terrorist material hosted in the UK or overseas.”