Liege, an industrial city close to the German border in a French-speaking region, was the scene of a shooting in 2011, when a gunman killed four people and wounded more than 100 others before turning the gun on himself.

On its travel advice website, the UK’s Foreign Office warns holidaymakers that terrorists are “very likely” to carry out attacks in Belgium.

The website states: “Attacks could happen anywhere, including on public transport and transport hubs and in other places visited by foreigners.”