400 Isil bombers 'trained to carry out attacks across EU'
Isil has trained at least 400 fighters to target Europe in deadly waves of Brussels-style attacks, deploying terror cells with orders to choose the time, place and method for maximum carnage, according to jihadi experts.
The network of agile and semi-autonomous cells shows the reach of the extremist group in Europe even as it loses ground in Syria and Iraq.
Jihadi experts, including European and Iraqi intelligence officials and a French lawmaker who follows the terror networks, described camps in Syria, Iraq and possibly the former Soviet bloc where attackers are trained to attack the West.
Before being killed in a police raid, the ringleader of the Paris attacks claimed to have entered Europe in a multinational group of 90 fighters, who scattered "more or less everywhere".
But the biggest break yet in the Paris attacks investigation - the arrest on Friday of fugitive Salah Abdeslam - did not thwart the multipronged attack just four days later on the Belgian capital's airport and metro that left 31 people dead and an estimated 270 wounded.
Three suicide bombers also died.
Just as in Paris, Belgian authorities are still searching for at least one fugitive in Tuesday's attacks - this time for a man seen on security footage in the airport with the two suicide attackers. The fear is that the man, whose identity Belgian officials say is not known, will find Abdeslam's path instructive.
After fleeing Paris immediately after the November attacks, Abdeslam forged a new network back in his childhood neighbourhood of Molenbeek, long known as a haven for jihadis, and renewed plotting, according to Belgian Foreign Minister Didier Reynders.
"Not only did he drop out of sight, but he did so to organise another attack, with accomplices everywhere. With suicide belts. Two attacks organised just like in Paris. And his arrest, since they knew he was going to talk, it was a response: 'So what if he was arrested? We'll show you that it doesn't change a thing'," said French Senator Nathalie Goulet, co-head of a commission tracking jihadi networks.
Estimates range from 400 to 600 Isil fighters trained specifically for external attacks, according to the officials, including Ms Goulet. Some 5,000 Europeans have gone to Syria.
"The reality is that if we knew exactly how many there were, it wouldn't be happening," she said.
Two of the suicide bombers in Tuesday's attacks, brothers Ibrahim and Khalid Bakraoui, had no known extremist links until an apartment one of them rented was traced to Abdeslam last week, according to Belgian state broadcaster RTBF.
Similarly, an Algerian killed inside that apartment on March 15 had nothing but a petty theft record in Sweden - but he'd signed up as an Isil suicide bomber for the group in 2014 and returned to Europe as part of the November 13 plot to attack Paris.
In claiming responsibility, Isil described a "secret cell of soldiers" dispatched to Brussels for the purpose.
The shadowy cells were confirmed by Europol - the EU police agency which said in a late January report that intelligence officials believed the group had "developed an external action command trained for special forces-style attacks."
French speakers with links to North Africa, France and Belgium appear to be leading the units and are responsible for developing attack strategies in Europe, said a European security source.