The Belgium government sought Sunday to contain criticism of its handling of the Brussels attacks, as investigators launched 13 anti-terror raids in the capital and two other cities and taking four more people in custody.

In central Brussels, riot police used water cannon when scuffles broke out in front of the Bourse, which has become a symbolic rallying point for people to pay their respects to those who died in Tuesday’s suicide bombings. Black clad men carrying an anti-Islamic State group banner with an expletive on it held an agitated rally, but were pushed back by riot police.

Interior Minister Jan Jambon conceded Sunday that decades of neglect had hampered the government’s response to violent extremism. He said the government has invested 600 million euros ($670 million) into police and security services over the past two years but that Belgium’s justice system and security services are still lagging behind.

Jambon, whose offer to resign Thursday was declined by the prime minister, also acknowledged some shortcomings prior to the March 22 suicide bombings in Brussels that killed at least 31 people and wounded 270 others.

“There have been errors,” he said on VRT television.

Jambon said it takes time to hire anti-terror specialists and specialized equipment and insisted that the government’s new investments need time before they become visible to the public.

Federal prosecutors, meanwhile, said Sunday morning’s raids were linked a “federal case regarding terrorism” but did not specify whether it had any links to the March 22 attacks.

The 13 raids were launched in the capital and the northern cities of Mechelen and Duffel. An investigating judge will decide later whether the four will remain in custody. Five were released after questioning.

As international pressure on Belgium has mounted for serving as an unwitting rear-base for extremist fighters who launched the Nov. 13 massacres that left 130 dead in Paris, the government has felt forced to defend its choices and the actions of investigators. Lawmakers, meanwhile, are demanding an inquiry.

Belgian police and the army have been deployed, sometimes around the clock, at major buildings and sites in the capital in increasing numbers since November, when Brussels went into lockdown over fears that top Paris suspect Salah Abdeslam had returned and was hiding there.

As it turned out, Abdeslam did return, but police did not find and arrest him until March 18, four days before suspects from his network exploded suicide bombs in Brussels.

Belgian investigators have been slammed for not questioning Abdeslam long enough or hard enough after he was shot in the leg during his arrest. Police have also been criticized for taking too long to get to Zaventem airport on Tuesday morning after two suicide bombers blew themselves up there — and left an even bigger third suitcase full of explosives that did not go off.

Jambon and Justice Minister Keen Goens were grilled by lawmakers Friday over how authorities failed to arrest suicide bomber Ibrahim El Bakraoui before he blew himself in the packed departure hall at Brussels Airport.

Turkey has said that Bakraoui — whose brother Khalid was the suicide bomber at the Maelbeek subway station on Tuesday — was caught near Turkey’s border with Syria in 2015 and Ankara had warned Brussels and the Netherlands that he was “a foreign terrorist fighter.” Belgian authorities said they did not know he was suspected of terror-related activities until after he was deported to the Netherlands.

Jambon also said the Brussels subway network had been told to shut off services around 20 minutes before the attack at the subway station, which is close to both the European Union headquarters and the U.S. embassy. He did not fully explain why it was not closed in time, raising more questions about the efficiency of Belgium’s security services.

On Sunday, Italian police in the southern city of Salerno said they had arrested an Algerian wanted in Belgium for an alleged false ID crime ring facilitating illegal migration linked to the attacks in Paris. Djamal Eddine Ouali was arrested Saturday in the town of Bellizzi, said Luigi Amato, the head of Salerno police’s anti-terrorism squad. Ouali, 40, was being held in jail while authorities expect extradition procedures to soon begin.

At the Maelbeek subway station, messages of sadness, solidarity and grief left for victims of the bomb attack there were being collected for storage in the Belgian capital’s archives. The messages were laid out on absorbent paper to dry after overnight rain and carefully stacked for transport. Those that can’t be taken for safekeeping were being photographed.

“We are trying to collect as many documents we can find and they will be preserved,” promised head archivist Frederic Boquet.

Marina Queralt, who often walks with her dog by the Maelbeek station, said the public response to the attacks has been focused on peace.

“Every morning, every afternoon, (the site) was packed with people who wanted just one thing: that people stop killing each other,” she said.

(AP)