Police arrested four people yesterday after raids in Jumet, near the southern city of Charleroi, on suspicion that they planned to go to either war-torn Syria or Libya.
A spokesman for the federal prosecutor confirmed that three had been charged for links to a terrorist organisation and were now being held in preventive detention.
The spokesman said the fourth person had been freed after questioning.
Press reports said the three included a couple which had become radicalised recently.
Of the couple, the man aged 23 and a convert to Islam had told police he wanted to travel to Syria to do humanitarian work.
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Belgian police have arrested 11 people in connection with the November 13 attacks in Paris which left 130 people dead and hundreds wounded as it emerges that the onslaught was largely organised and coordinated from Belgium.
Earlier this month, the authorities identified three safe houses used by key Paris suspects -- in Brussels, in Charleroi, an hour's drive south of the capital, and in Auvelais, a village near the French border.