Belgium: Unlikely Hotbed for Terror in Europe

Just a day before explosions in Brussels killed more than 30 people and injured at least three Americans, top Belgian officials knew they were in trouble.

"We are far from putting the puzzle together," Belgian prosecutor Frederic Van Leeuw told reporters Monday morning, hours after authorities captured an alleged ISIS operative suspected in November's Paris attacks. The nation's interior minister, Jan Jambon, told a local news outlet that the man's purported terror network was "bigger than we thought in the beginning" and that he clearly had logistical support in the heart of Europe -- a network that threatened more carnage.

"When weapons and terrorists are in the same place, it means there's going to be an attack," Jambon said.

A day later, at least three explosions ripped through a Belgian airport and metro station, killing more than 30 and injuring over 100 others, and the Syria-based terrorist organization ISIS -- the same group that is believed to have carried out the Paris attacks -- released a statement claiming responsibility.

"They [Belgian authorities] were unable, during all of that four months, to find the [suspect in] the Paris attacks and they were unable over the course of the weekend and through Monday to stop this new cell that they knew was out there," Richard Clarke, former White House counter-terrorism advisor and current ABC News consultant, said.

Belgium, and Brussels in particular, came to world's attention as a surprising home to extremism in the days after the Paris attacks in November, when French President Francois Hollande declared the attacks that killed 130 of his countrymen was "organized" there. But at the time terrorism analysts and experts told ABC News that Belgium had a long, troubled history with terrorism and that for the most part the country was slow to respond.

"There has been a serious jihadi issue there for many, many years," Daniel Benjamin, who oversaw State Department counter-terror efforts during President Obama's first term, told ABC News then. "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."

Belgium has served as a European pipeline for extremists looking to join ranks with ISIS, experts said. 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. An official estimate in October 2015 put the number at 470.

Howard Gutman, a veteran Washington lawyer who served as U.S. Ambassador to Belgium until 2013, told ABC News in November 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 said then. "So they cannot watch even a fraction of the high risk threats."

"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."

Since the Paris attacks, Belgium kicked its law enforcement actions into high gear, making more than 50 arrests and raiding more than 100 houses, according to local officials. There was so much action that several terrorism experts told ABC News Friday that ISIS's presence in Belgium was likely "decimated."

But Belgian officials made it clear Monday they did not consider the crisis averted and even predicted a tragedy like today's may come to pass.

"We're worried that [Paris attacker Salah] Abdeslam's arrest will activate other terror cells," Jambon told reporters Monday.

A former military official told ABC News he suspected that's exactly what happened - that ISIS was planning a terror attack in Belgium and were forced to move up their timeline after Abdeslam was grabbed, fearing he would give up the plot.

"The reason that they attacked now is probably that they thought their cover was being blown," agreed Clarke, the former White House counter-terror advisor. "Last week there were two raids in Brussels, several of them were rounded up, some of them were under interrogations. The Belgian authorities knew that there was a plot underway, they didn't know what it would be."