The Islamic State's English-language magazine Dabiq shows Belgian Abdelhamid Abaaoud. (Uncredited/AP)

French security forces scrambled on a surprising lead: The man considered to be the ringleader of the Paris attacks — an Islamic State operative and the puppet master of its effort to terrorize Europe — was hiding out right under the noses of French intelligence.

Two senior European officials familiar with the investigation said they received confirmation Wednesday from the French that one of the dead was the high-profile target: Abdelhamid Abaaoud, a 28-year-old Belgian of Moroccan descent who cajoled his own 13-year-old brother into fighting in Syria.

French officials confirmed Thursday that Abaaoud was killed during the seven-hour siege north of Paris, which included a woman detonating a suicide blast. Eight others were taken alive.

Abaaoud’s ability to successfully traverse the porous borders of Europe and hide in France raises worries that reach beyond the current manhunt for suspects after last week’s Paris attacks. It suggests just how large a security threat the entire continent could be facing.

Officials think the man who has boasted of easily escaping “crusader intelligence” as he sneaked in and out of Europe is a guru behind the Paris massacre. In the hours and days after the attacks — which struck a stadium, a concert hall, bars and restaurants — authorities have pieced together a picture of a network of attackers with ties that radiate back to Abaaoud.

Two European officials familiar with the case said Abaaoud is thought to have arrived in Syria sometime in 2013 or 2014 and to have slipped in and out of Europe since. Following the Paris attacks, the intelligence community was divided on where Abaaoud might be. Some officials believed he might be in Syria. But Paris prosecutor François Molins said Wednesday that investigators received information from a witness Monday that Abaaoud was in France.

“It was taken very seriously and was double-checked through the verification of phone records and banking operations,” he said.

At least two of the men believed to be directly involved in the Paris attacks — including Salah Abdeslam, a 26-year-old who is on the run — had years-long connections to Abaaoud and came from the same hardscrabble neighborhood in Brussels that has become a breeding ground for European jihadists. The bearded Islamic State operative, officials say, may also have been directly involved in the recruitment of other assailants in Friday’s attacks, and he was actively involved in several other attempts this year to stage terrorist acts in Europe.

Abaaoud has been linked by authorities to several foiled terrorist plots in France and Belgium over the past two years, including the attempted attack in August on a Paris-bound high-speed train from Amsterdam that was thwarted with the aid of three Americans.

In August, Reda Hame, a French foreign fighter, was arrested in France after returning home from Syria. He told the police that he had met Abaaoud in Syria and had been instructed to strike at densely populated targets. He said he had been given several targets for attacks in France, including “concert halls” and “food markets.”

Authorities say as many as 20 people may have been involved in the plot to attack Paris. Here's what we know about them so far. (Gillian Brockell/The Washington Post)

“These weren’t specific targets,” a French official said, “rather, ideas of places to strike, so as to spread fear everywhere.”

Abaaoud spent his youth in the Molenbeek neighborhood of Brussels and was arrested for petty crimes — a profile common among young jihadists who were also wayward youths. But he is thought to have later associated with members of Sharia4Belgium, an Islamist activist group that was designated a terrorist organization this year.

Abaaoud is believed to have joined the Islamic State sometime in 2013. He has appeared in a number of its videos, including one from March 2014 in which he drives a pickup truck with a string of dead bodies attached.

“He contributed to sending hundreds of Belgians to Syria, coordinating departures,” said Jean-Charles Brisard, a counterterrorism expert based in Paris. “He has a big role in recruitment of the French-speaking jihadists.”

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