The announcement of a formal Islamic state by insurgents in Syria and Iraq is a "declaration of war against the West and al Qaida", an expert has warned. The Islamic State in Iraq and Greater Syria (Isis) group has sought to solidify its leadership of worldwide jihad today by declaring that its leader, Abu Bakr al-Baghdadi, is the new caliph, or head of state.
Abu Mohammed al-Adnani, a spokesman for the group, called for those living in the area under the group's control in both countries to swear allegiance to Baghdadi.
Around 500 British-linked citizens are already thought to have travelled to the Middle East to fight with the Sunni Muslim group against its Alawite and Shia sectarian foes amid fears that more will join them.
Professor Peter Neumann, from the International Centre for the Study of Radicalisation at King's College London, said the significance of today's announcement should not be underestimated. "It's a declaration of war - not only against the west and all the countries that are currently fighting Isis, but more importantly, against al-Qaida. Isis now see themselves as the legitimate leaders of the movement and they expect everyone to fall in line.
"For ideological jihadists, the caliphate is the ultimate aim, and Isis - in their eyes - have come closer to realising that vision than anyone else. On that basis, Isis leaders believe they deserve everyone's allegiance.
"This could be the end of al-Qaida. It depends on how they respond. Unless they come out fighting, this could mark the end of Bin Laden's vision and his legacy."
Neumann said the declaration of a caliphate showed how confident Isis are after making spectacular gains in Iraq in recent weeks following a spectacular collapse by government forces. "They haven't lost any of the momentum they gained when capturing Mosul," he said. "On the contrary, they've held on to it, gained more territory, and have seen jihadists from other groups swear allegiance to them.
"They must think their dream of creating the caliphate is finally coming true, and it's coming true faster and more dramatically than even they expected."
Islamic extremists have long aspired to recreate the Islamic caliphate that ruled over the Middle East for hundreds of years.
Over the last two weeks there has been growing concern over the number of young British Muslims who have joined Isis. David Cameron claimed that they represent the "biggest threat to national security that exists today".
Several youths who are believed to have travelled to the Middle East to fight have been identified, rocking Muslim families and communities in towns such as Cardiff, Aberdeen and Coventry.
The security services have made tracking British jihadists fighting in the region their top priority after a video emerged showing Britons filmed in Syria urging UK Muslims to join insurgents there and in Iraq.