Two surveillance cameras film St. Peter’s Square during a Palm Sunday Mass celebrated by Pope Francis, at the Vatican. (Giuseppe Lami/AP)

Even before Islamic State militants killed at least 31 people this past week in Brussels, the symbolic heart of Europe, governments across the continent were moving to bolster security by expanding already robust surveillance powers.

But the carnage in the Belgian capital, and the likelihood of continued terrorism plots, have failed to extinguish a sharp debate across Europe over augmented law enforcement and communications monitoring. Critics fear that such measures as enhanced government access to personal data or passenger records will impinge upon Europeans’ privacy without breaking down the barriers that have undermined anti-terrorism efforts in the past.

“People are misled into thinking that if they give up more privacy, they will get more security,” said Sophia in ‘t Veld, a Dutch member of the European Parliament who has opposed efforts to expand monitoring of personal data. “That is a complete illusion.”

The March 22 attacks in Brussels, seat of the European Union and NATO, intensified public anxiety about the reach of groups such as the Islamic State, which has vowed to exact revenge for the West’s military campaign in Iraq and Syria.

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The Belgian government is now being criticized for failing to detect the terrorist plot, which involved several individuals known to Belgian authorities. One of the attackers, Khalid el-Bakraoui, had been detained by authorities in Turkey on suspicion of terrorism in 2015 before being deported to Europe, where he went free.

The bloodshed in Brussels came just days after Belgium arrested Salah Abdeslam, one of the men involved in the Nov. 13 Paris attacks. Abdeslam evaded capture for months before he was apprehended blocks from his family’s home.

James Lewis, a senior fellow at the Center for Strategic and International Studies in Washington, said recent attacks, such as those in Paris, had spurred European governments, which already function with fewer checks than the United States does, to push for new monitoring powers.

But Lewis said long-standing bureaucratic barriers between the 28 E.U. member states, which view security as a primarily national matter rather than a European one, remained an important obstacle to successful defenses in Europe. Like the stove-piping of information that crippled the U.S. government’s awareness before the 9/11 attacks, European security services don’t share intelligence information effectively, he said.

“None of these systems are foolproof,” Lewis said. “It would be better if they played as a team, but Europe isn’t there yet.”

Top American security experts such as Michael V. Hayden, former director of the National Security Agency and the Central Intelligence Agency, have said European nations have long relied on the United States as a conduit for sharing information. That coordination role has been diminished, experts say, since Edward Snowden’s revelations about U.S. spy programs.

Lewis, who supports increased surveillance activities, said that even countries such as France lack adequate resources as they move to expand already active monitoring programs.

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Last summer, six months after militants inspired by al-Qaeda stormed a satirical magazine in Paris, French lawmakers approved a broad surveillance law, which allows phone taps and hidden cameras without a warrant. The law was aimed at stopping not only terrorist violence but also economic or criminal attacks. Then, in the wake of the November Paris attacks, French President François Hollande declared a state of emergency including stepped-up police and search powers. Now, France is considering additional changes, including extending the state of emergency and a controversial measure that could revoke the French citizenship of terrorism suspects.

Adrienne Charmet, a French civil liberties advocate, said public support in France was rooted in a misplaced idea that such measures were needed to keep people safe. Opposition voices, she said, were not being heard in the debate over these measures.

“It’s very dangerous for fundamental rights,” she said.

In the United Kingdom, known for its widespread use of public surveillance cameras, lawmakers are considering a bill that would update surveillance rules. The proposal has already been criticized by civil liberties advocates and by technology firms.

Harmit Kambo, campaigns and development director at advocacy group Privacy International, said that provisions to retain Britons’ Internet browsing history would be intrusive and ineffective.

“The government has not made a case for how connection records will keep people safer,” Kambo said. “We reject that it’s a choice between privacy and security.”

One exception to the trend across Europe is Germany, where memories of East Germany’s all-powerful state security agency have made many people protective of their privacy. Germany’s influential role in the European Union may have a cooling effect on Europe-wide proposals, such as one that would provide access to airline passenger records.

Proponents of such steps say that the likelihood of additional Islamic State or other militant attacks means that there is no time for half-measures.

After this week’s violence in Brussels, Belgian Prime Minister Charles Michel promised to defend his country’s “values and freedom” while it confronts terrorist threats. A large number of Belgian citizens have traveled to Syria to take up arms.

His government has not yet said what steps it may take to pursue enhanced surveillance powers. The Belgian Interior Ministry did not immediately respond to requests for comment.

Ben Caudron, a professor of technology sociology in Brussels, said he expects there will be increased resources devoted to technology, such as cameras or surveillance software.

Bart Somers, the mayor of the Belgian city of Mechelen, said that his heavily Muslim area had managed to avoid the widespread alienation that has plagued minority communities in Brussels. He attributed that in part to steps his city had taken, including community policing and installation of cameras in public areas.

Today, Mechelen has 150 to 200 surveillance cameras, more than anywhere else in Belgium, Somers said. In Somers’s view, such steps have improved citizens’ sense of safety and their willingness to cooperate with authorities.

“They are small bricks in building a wall” against radicalization, he said.

Annabell Van den Berghe contributed to this report.

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Today’s coverage from Post correspondents around the world