A number of people are believed to have been injured after an incident at a military training base in West Wales.
A spokeswoman for the Ministry of Defence said "my understanding is that there are casualties" at Castlemartin Ranges in Pembrokeshire.
"As I understand it people have been injured," she said. "This is still being investigated and therefore it would be inappropriate to comment further."
Live firing was due to take place on the range from Monday to Friday, with night firing expected on Tuesday and Thursday.
A notice on the Government's website said the road from Bosherston to St Govan's Chapel and the footpath from St Govan's Head to Broadhaven would be closed every day.
Castlemartin, which has been under military control since the 1930s, is the only remaining UK Army range available for armoured units for direct-fire live gunnery exercises.