France and Belgium face an "imminent" terror attack from Isil commandos who left Syria a week ago and are already armed, according to a Belgian intelligence note cited by local media.

The chilling warning that two-men groups were on the verge of an attack emerged hours before the kick off of France's second Euro 2016 game against Albania in Marseille and a day after a Frenchman who killed a police commander in the name of Isil warned that the Euro tournament would become a "graveyard".

The note from Belgium's anti-terror unit to police and published by Dernière Heure newspaper, warned: "Combatants are thought to have left Syria around a week and a half ago to reach Europe via Turkey and Greece by boat without passports." It gave no specific dates.