They face charges of either fighting alongside jihadist groups in Somalia, having attempted to go to Somalia or Syria, or of having provided support to a Belgian-based recruitment operation.
All 19 face the charge of “belonging to a terrorist group.”
Khafi, 39, told the criminal court in Brussels that he had not taken part in fighting in Somalia and the Al-Shabab militants he met had not trusted the Belgians and had confiscated their passports, the Belga news agency reported.
Three of his associates are imprisoned there on charges of illegal entry but are expected to be sent back to Belgium shortly.
The Brussels trial, which is taking place under heightened security, comes amid mounting concern over the number of Belgians believed to be traveling to Africa, Syria and the Afghan-Pakistani border to fight alongside jihadist groups.