Counter-terrorism training noise alert for Kidwelly
A major counter-terrorism training exercise is being led by South Wales Police to test the response of emergency services to such an attack.
Scenarios are based on "prevailing" threats following attacks in France and Belgium, said the officer in charge.
The exercise over the next two days is being held at Ffos Las racecourse near Kidwelly, Carmarthenshire.
People have been told not to be concerned by noise of gun fire and explosions in the area.
South Wales Police Assistant Chief Constable Jon Stratford, who is leading the operation, said the UK Government's emergency response committee, Cobra, involving ministers and intelligence officers, would also participate.