Terrorists struck Brussels’ main international airport and a subway station Tuesday in Belgium’s deadliest terror attacks since World War II. ISIS has claimed responsibility.

Government officials put the death toll at at least 31, with more than 180 wounded. Belgium raised its terror alert to the highest level.

“We are experiencing the darkest day in the history of our country since the Second World War,” said Antwerp Mayor Bart de Wever, leader of Belgium’s largest political party.

The toll from the morning rush-hour attacks appears to be the highest in Europe since 130 people were killed in Paris in a series of attacks on November 13. Tuesday’s attacks followed Friday’s arrest of a man in Brussels, Salah Abdeslam, who was the main fugitive of the November killings in France.

“We were fearing terrorist attacks, and that has now happened,” Belgian Prime Minister Charles Michel said.

Brussels is the seat of Europe’s government — the city hosts the European council, commission and parliament. Thomas Hegghammer of the Norwegian Defence Research Establishment, a specialist in Islamist militancy, says that makes the Belgian capital especially important to terrorists.

And European and Belgian counterterrorism officials know that. Even still, Hegghammer thinks this situation is unprecedented. He says in the past, the issue was having too many potential threats and not knowing which to focus on.

“This is different,” he says. “You know who you are after, but you can’t find them. … There are still people on the run [from the Paris attacks]. … What worries me is that it is taking so long to apprehend them. You have known individuals that it takes months to capture.”

A soldier stands near broken windows after explosions at Zaventem airport near Brussels, Belgium, March 22, 2016.

Credit:

Francois Lenoir/Reuters

European counterterroriam officials said they were “very concerned” about terror attacks in a meeting last week, according Matt Levitt, who runs the Washington Institute’s Stein Prorgam on Counterterrorism.

“They were eager to tell me all the things they’ve put in place recently since the November attacks in Paris and even before then,” Levitt says. “But they were also — to their credit, I think — pretty open about how far they have yet to go. And I think it’s a lesson for all of us.”

Ordinary Belgians had begun to relax a bit after the arrest of Salah Abdeslam, says James Panichi, who is in Belgium covering the story for Politico.

“It was a feeling of elation I think. A lot of people felt that in a way they could relax, that this level of alert was in a way not entirely justified,”  Panichi said. “Well, that view has been shattered by these attacks. I think in many ways, Belgians hadn’t expected this and it really came as a shock.”

The neighboring nations of France, Germany and the Netherlands tightened border security immediately after the Brussels attacks, as did Britain.

Belgian police have issued a wanted notice for a man dressed in white.

The airport and metro system in Brussels have been closed. Social media drives have begun to offer shelter and rides to people stranded in the Belgian capital. 

The European Commission has told employees to stay indoors or at home. UK Prime Minister David Cameron and US Pentagon chief Ashton Carter denounced the attacks and said their nations stand ready to help Belgium.

President Obama, still on his official visit to Cuba, offered help, as well: “We can and we will defeat those who threaten the safety and security of people all around the world.”

David Beard, Jeb Sharp, David Leveille and Christopher Woolf from PRI’s The World contributed to this report.

From PRI’s The World ©2015 Public Radio International