Thalys attack France
French police in protective clothing collect clues inside the Thalys high-speed train on which a man attempted to launch a terror attackReuters

Six men arrested in connection with the August 2015 attack on a high speed train travelling from Amsterdam to Paris have been released without charge.

Two people were injured by the Kalashnikov-wielding attacker on the train before he was overpowered by passengers.

"They were released as planned after some checks," a spokesman for the Belgian federal prosecutor told Reuters. "There were no charges, either."

Four of the men who foiled the train attack were subsequently awarded France's highest honour, the Legion d'honneur. The alleged perpetrator, Ayoub el Khazzani, remains in police custody ahead of his trial on terror charges.

Belgium remains on a state of high alert following the 22 March terror attacks on Brussels airport and a metro station in the city in which 32 people were killed.

Early on 21 June, a man reportedly wearing a fake suicide belt sparked a terror alert in a Brussels shopping centre. Prime Minister Charles Michel described the situation as "under control" after a meeting of the national crisis response centre.

The arrests followed police raids on several properties in Brussels, which saw three men charged for planning a terror attack. Belgian media reports the three planned to attack fans at the Euro 2016 football tournament in France.

No explosives or weapons were found in the raids that resulted in the arrest of the six now released, said police.