A number of people are believed to have been injured following an incident at a military training base in West Wales, the Ministry of Defence (MoD) has said.
A spokeswoman for the MoD said it was aware of the incident at Castlemartin Ranges in Pembrokeshire.
She said: "My understanding is that there are casualties. As I understand it people have been injured."
A firing notice for Castlemartin on the Government's website suggests live firing was due to take place on the range from Monday to Friday.
A notice 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.
The notice adds that night firing was due to take place on Tuesday and Thursday.
The MoD spokeswoman added: "This is still being investigated and therefore it would be inappropriate to comment further."
According to the Visit Pembrokeshire website, a large part of the Castlemartin peninsula was taken over by the Royal Armoured Corps (RAC) tank range in the late 1930s and further developed during the Cold War period.
It is now the only UK Army range available for armoured units for direct-fire live gunnery exercises.