Belgian police held four people Monday over the 2015 train attack on a high-speed Thalys train linking Brussels and Paris in which a Daesh terrorist shot and seriously wounded a passenger before being overpowered.

Police raided six properties around Brussels and "four people were taken in for questioning", Belgian prosecutors said in a statement. An investigating judge will decide later what further action to take against the detainees.

In August 2015 a machinegun-toting attacker wounded three people on a high-speed train before being overpowered by passengers, one in a series of terrorist attacks that has rocked Belgium and France over the past two years.

Police carried out six house searches in Brussels and elsewhere in Belgium early Monday, but did not find any explosives or weapons.

A judge will decide at a later stage whether those detained could be kept further, prosecutors said.