— -- As heavily-armed police today raced around Brussels chasing leads related to the horrific terrorist attacks in Paris, terrorism experts and analysts told ABC News the chaos in the normally-buttoned downed capital was proof that Belgium can no longer afford to be slow-footed in the small nation’s fight against the outsized presence of radical Islam.
“There has been a serious jihadi issue there for many, many years,” said Daniel Benjamin, who oversaw State Department counter-terror efforts during President Obama’s first term. “A number of European countries have underestimated the threat and have been in denial about the dangers they faced… The Belgians especially were in denial.”
Today French President Francois Hollande said that the suicide terror attacks that claimed more than 120 lives in Paris had been “organized” in Belgium, and over the weekend two men were arrested in the Molenbeek district of Brussels and charged with terrorism-related offenses. Officials said Brussels is also home to at least two of the suicide bombers. One of them, as well as a man more recently identified as the suspected “mastermind” of the attack, was from Molenbeek.
The purported mastermind, Abdelhamid Abaaoud, was previously linked to smaller terror plots in Europe, including foiled European train and church attacks earlier this year. After a gun-battle with police in another Belgian suburb that reportedly killed two suspected extremists in January, he told an ISIS magazine he was able to escape into Syria. He’s believed to still be there, where one French official said he’s considered a “high-profile terrorism figure.”
In the days leading up to Friday’s violence, the Belgian cell purportedly procured the rental cars used in the attack and may have supplied the weapons and explosive vests. At least one of those involved escaped back over the France-Belgium border after the attack and is now the subject of a massive manhunt, European officials said. He was thought to have been surrounded by police in Molenbeek, but the police raid revealed he wasn’t there after all.
"We're talking about a network," the Molenbeek’s mayor, Francoise Schepmans, said in a Reuters report Sunday, referring to individuals arrested there.
Before the Paris massacre last week, the Belgian capital and often the specific district of Molenbeek repeatedly have found themselves playing a supporting role in past plots. After 12 people were killed by three gunmen in the Charlie Hebdo attacks in Paris in January, authorities raided locations in Molenbeek and other Belgian cities in during an investigation purportedly unrelated to the shootings that nevertheless “concerning several people who [Belgian authorities thought] are an operational cell” made of people who had been in Syria. Other reports said one of the Charlie Hebdo gunmen got his weapons in Molenbeek.
The young man who attempted to open fire on a French train earlier this year reportedly stayed for a time in Molenbeek before the attack. And greater Brussels was the site of an attack on a Jewish museum in May 2014 that claimed four lives.
Belgian Prime Minister Charles Michel expressed deep concerns this weekend about the scope of the problem facing his country.
“Almost every time, there is a link to Molenbeek,” Michel said. “We have to clean up that terrorism in Molenbeek . That’s the main issue here.”
Residents and politicians of the small district are becoming exasperated with its reputation, according to Germany’s Der Spiegel.
“They don’t all come from here,” district Mayor Schepmans told the paper. “Most of the time, they are just traveling through.”
Security experts told ABC News that the jihadists in the most recent attack took advantage of an intelligence and security apparatus in Belgium that was slow to recognize and respond to the threat, and remains poorly equipped to monitor those plotting future attacks.
Belgium has served as a European pipeline for extremists looking to join ranks with ISIS. About six percent of Belgium’s population is Muslim, but conditions in the country have produced the largest number, per capita, of foreign fighters traveling to Syria or Iraq to join ISIS and other extremist groups.
A 2014 estimate by a Belgian researcher who tracks extremist activity there put a conservative estimate of the number of Belgian foreign fighters at 400, but indicated that number could actually be twice as high.
The potential for ISIS sympathizers in Brussels to pose a danger to the rest of Europe has been a longstanding concern of the U.S., Benjamin said.
“My impression is that Belgian authorities have been taking the threat more seriously as time has gone by,” Benjamin said. “But I don’t believe they have the capacities of the British or the French.”
Howard Gutman, a veteran Washington lawyer who served as U.S. Ambassador to Belgium until 2013, said the Belgians began updating their laws over the past decade to enhance their ability to monitor extremists.
But they have continued to struggle to keep pace with the growing ranks of disaffected young Muslims who fled Syria after President Assad used chemical weapons in recent years.
"There are probably 500 prime targets, which would require 5,000 agents to keep proper tabs. My best guess is that the Belgian [elite security] force probably totals about 200," Gutman told ABC News. "So they cannot watch even a fraction of the high risk threats."
Gutman said helping Belgium reach out to the large population of young Muslims was a high priority during his time in the Embassy.
"We had significant success," he said. "I visited every major mosque and Muslim community centers and established relations with the imam and in the community including in Molenbeek. For many of these visits, I was the only Western and non-Muslim visitor they had ever had."
Shortly before the attacks, Belgian Interior Minister Jan Jambon appeared at a conference sponsored by the news web site Politico dealing with extremism. The news site quoted Jambon saying that his country was getting a better handle on the problem in most Belgian cities, but said the exception was Brussels. He blamed a fragmented police force.
“Brussels is a relatively small city, 1.2 million,” Jambon told Politico. “And yet we have six police departments. Nineteen different municipalities. New York is a city of 11 million. How many police departments do they have? One.”
Two months ago, Jambon released a 12-point plan to strengthen the monitoring of Islamic radicals, expressing confidence in the country’s handle on the problem. But this week, Prime Minister Michel said that those efforts were insufficient.
“There has to be more of a crackdown,” Michel said.
CORRECTION: This report has been updated to say that two suspected extremist reportedly were killed in the January shootout by police. The original report included an error introduced during the editing process that said two policemen had been killed in that incident.
Get real-time updates as this story unfolds. To start, just "star" this story in ABC News' phone app. Download ABC News for iPhone here or ABC News for Android here.