THE ringleader of the Paris attacks was able to slip into Europe among Syrian migrants, it emerged last night (THursday night), as police on the continent admitted they are unable to monitor thousands of suspected jihadists.
EU interior ministers will today move to tighten the continent's borders to ensure that every single migrant is checked against a terror watchlist, after French authorities revealed that Abdelhamid Abaaoud was able to return from Syria via the migrant route through Greece.
At a summit in Brussels, they are also expected to bow to French demands to screen every single EU passport holder entering the continent for the first time to catch fighters returning from the Middle East.
Europol, the organisation that polices Europe's external border, yesterday admitted that only 2,000 of the estimated 5,000 extremists who have travelled to Syria and Iraq to wage jihad have been logged on an EU-wide intelligence sharing database used by Britain to disrupt plots. It means Britain has no way of checking the background of 3,000 suspected terrorists, even if their own country has identified them as a threat.
One French official said the EU's borders were "like a sieve".
It came as Manuel Valls, the French prime minister, and US intelligence officials warned the Islamic State of Iraq and the Levant (Isil) could use chemical or biological weapons.
Yesterday it emerged that Abaaoud and at least two of the Paris terrorists took the migrant route via Greece, intensifying fears that terrorists are able easily to exploit the refugee crisis to get to Europe.
Bernard Cazeneuve, the French interior minister, said French intelligence was unaware Abaaoud was in the country until after the massacre, and said other states had provided no intelligence on his whereabouts. He demanded that Europe "pull itself together".
A senior member of the DGSE, France's equivalent of MI6, said: "It has to be said: Schengen is a sieve. A guy with a CV and history like this, wherever he turned up in Schengen, he should have sparked a red flag."
Europe's interior ministers are expected to agree to a security crackdown on the external borders of the Schengen zone at a summit in Brussels today.
Under emergency EU plans seen by The Daily Telegraph, every traveller into the Schengen zone will have their details checked against the Schengen Information System (SIS) watchlist - a database accessed by all EU countries including Britain - to monitor extremists and other criminals.
At present, only non-EU passport holders are meant to have SIS checks. EU passport holders only undergo a cursory visual passport inspection, to respect their "freedom of movement".
Up to six of the eight Paris attackers fought in Syria, and Abaaoud had boasted to an Isil magazine of how police failed to catch him as he moved several times between Belgium and Syria, with border guards failing to recognise his face as a wanted man.
As part of the crackdown, every single refugee entering Europe will also be subject to a full SIS check for the first time, according to a leaked text of the draft conclusions.
Officers from Europol will be deployed to landing grounds in Greece and Italy to screen out potential terrorists.
Rob Wainwright, the director of Europol and a former intelligence officer in MI5, yesterday admitted weaknesses in the Focal Point Travellers system, the EU-wide database for sharing details of known jihadists between intelligence agencies in order to disrupt plots.
It contains the movements of 2,000 confirmed foreign fighters, along with 8,000 associates or "facilitators".
"We are only confident we have 2,000 names in the system, even though the general assessment across Europe is there are at least 5,000 European nationals who have travelled to Syria and Iraq," he told a committee of MEPs. The majority of the data is supplied by just a handful of states, he said.
Mr Wainwright disclosed that the security agencies are "urgently scrutinising" links between migrant smuggling gangs and the Paris terrorist cell.
"We all have seen in the media the reports of possible connections with, for example, a stolen Syrian passport. What this indicates, perhaps, is connection with the migration crisis, or illegal rings of people smugglers.
"It is too early for us to confirm this link exists, but Europol is prioritising its focus on trying to determine that at this moment."
In the latest sign that the Schengen-free travel zone is on the brink of collapse, the Netherlands yesterday proposed the creation of a mini-Schengen, comprising itself and Belgium, Luxembourg, Germany and Austria.
There would be migrant transit camps set outside these borders, and checks on anyone attempting to enter. Germany condemned the idea.
Charles Michel, the Belgian prime minister whose country is accused of turning a blind eye to a series of plots, said extremists would be electronically tagged. He added: "For jihadis who return, their place is in prison."
Meanwhile, Nicola Sturgeon, the Scottish First Minister said she was "prepared to listen" to the case for the UK launching air strikes on Syria, but insisted it was "incumbent" on David Cameron to make the case for this before any attack. The SNP leader said last month that her party would oppose this use of force, arguing that what is needed "is not more bombing, but a renewed and intensive diplomatic initiative".
But in the wake of Friday's attacks she said she would consider the matter. Ms Sturgeon told BBC Scotland: "I'm prepared to listen. Given what is happening, what has happened, I think it would be irresponsible not to do that.
"But I think it is incumbent on the Prime Minister, if he is going to bring a proposal for air strikes to the House of Commons, that he makes that case and he addresses that case to these key points."