Belgians returning from jihad in Iraq and Syria will be detained in the future, Prime Minister Charles Michel has announced.

Michel also told parliament in Brussels that his government would budget an additional €400 million for security spending after Belgian nationals were identified as suspects in Friday’s terrorist attacks in Paris.

Other new counterterrorism measures include speeding up trials for returning foreign fighters and banning the anonymous sale of phone sim cards.

Relatively more citizens of Belgium have traveled to the Middle East to join the self-declared Islamic State’s holy war there than from any other European country. Some 500 have returned.

As Michel was speaking in parliament, Belgian police launched raids across Brussels to find persons associated with the Paris attacks for which the Islamic State claimed responsibility.

Investigations have centered on the city’s predominantly Muslim-populated neighborhood of Molenbeek.

The ringleader of Friday’s attacks, a 28 year-old Belgian militant, was killed in a police raid in a suburb of Paris on Wednesday.

Belgium is part of the Arab-Western coalition that carries out airstrikes against Islamic State militants in Iraq, but it has so far stopped short of also bombing in neighboring Syria.