ISIS are using sophisticated fake Syrian and Iraqi passports to smuggle jihadists into Europe amid the migrant crisis, British intelligence has warned.

Extremists are exploiting the flow of migrants into Europe by posing as refugees and using new identities to avoid detection by border officials, officials say.

The warning has sparked fears terrorist sleeper cells are being set up in Britain and other EU nations.

ISIS are using sophisticated fake Syrian and Iraqi passports to smuggle jihadists into Europe amid the migrant crisis, British intelligence has warned (file picture)

The false passport in the name of Ahmad al-Mohammed (left) was found at the Stade de France after the Paris terror attacks and was registered in the Greek island of Leros. Fellow ISIS suicide bomber Bilal Hadfi (right) is also thought to have illegally returned to Europe to help carry out the massacre

Intelligence and security agencies are said to be 'very mindful' of the possibility that ISIS are using refugee routes across the continent, the Daily Telegraph reports.

A senior British intelligence official told the newspaper: 'Islamic State is skilfully exploiting the migrant crisis to smuggle terror cells from Syria into major European countries such as the UK.

'Jihadists travel to Raqqa to meet up with (ISIS) commanders, where they receive training and new passports.

'They then make their way back to Europe posing as migrants with new identities, making it virtually impossible for security officials to detect potential terrorists among those fleeing persecution.'

Hundreds of Britons are said to have made their way to join ISIS - and there are fears many have since returned to the UK.

The chairman of the commons home affairs committee, Keith Vaz, described the issue as 'deeply concerning' adding that it was 'vital' that resources were found to 'secure the external border' to prevent Paris-style atrocities.

The chairman of the commons home affairs committee, Keith Vaz (pictured), described the issue as 'deeply concerning'

The French interior minister Bernard Cazeneuve (pictured) warned ISIS has formed an entire 'industry' out of making fake passports stolen in Iraq

It comes a day after French officials warned ISIS has formed an entire 'industry' out of making fake passports stolen in Iraq, Syria and Libya.

The French interior minister Bernard Cazeneuve made the claim as he argued for the creation of a special task force to travel to Greece to help clamp down on stolen or fake passports.

At least two of the ISIS extremists who launched a murderous attack in Paris in November are suspected to have used established migrant routes through Europe pretending to be refugees and using Syrian passports.

The forged documents were found at the scene of one of the suicide bomb attacks at the Stade de France, further fueling speculation that ISIS may have a ready source of blank passports.

Some analysts at the time of the attacks suggested that the discovery of the Syrian passports was in no way conclusive that the jihadis had used them to enter Europe.

The documents may have been deliberately planted to stir up hatred and distrust towards migrants, particularly refugees fleeing the war in Syria.

Slovak prime minster Robert Fico suggested the EU was committing 'ritual suicide' with its migration policy

Yesterday, the Slovak prime minster Robert Fico suggested the EU was committing 'ritual suicide' with its migration policy.

He urged the 28-member bloc to stop the inflow of migrants and called the EU's proposed quota system for distributing migrants a 'complete fiasco'.

His warning came as the Netherlands' EU commissioner Frans Timmermans claimed 60 per cent of those flocking to Europe were economic migrants and not fleeing from war.

The 51-year-old Slovak leader, a left-winger known for his anti-immigrant rhetoric, told Czech newspaper Pravo: 'I feel that we in the EU are now committing ritual suicide and we're just looking on.'

Holland's EU commissioner Frans Timmermans claimed more than half of those coming to Europe as asylum seekers are not fleeing conflict.

He told Nos: 'More than half of the people now coming to Europe come from countries where you can assume they have no reason whatsoever to ask for refugee status. More than half, 60%.’