BRUSSELS

Belgian police raided 22 houses across the country on Friday as part of an anti-terror operation, arresting four people, according to the country’s federal prosecutor.

Police did not find any arms, explosives or ammunition in the raids which targeted properties in several Belgian cities including northern Antwerp and the capital, Brussels.

The raids were carried out as part of an investigation into people suspected of planning to travel to Syria to fight with terror organizations.

Belgian authorities have said anti-terror raids in Verviers and the Paris attack earlier this month have no connection to Friday’s operation.

According to the International Centre for the Study of Radicalisation and Political Violence, just under 300 people left Belgium in the two years up to December 2014 to fight in Syria.

According to the London-based think tank, Belgium was one of the most heavily affected countries in Western Europe, supplying 27 fighters per million people of their population.