A number of people are believed to have been injured in a tank incident at a military training base in Pembrokeshire.
The Welsh Ambulance Service was called to Castlemartin firing range just before 15:30 BST on Wednesday.
A Ministry of Defence spokeswoman said: “We are aware of an incident at Castlemartin ranges.
“This is still being investigated and therefore it would be inappropriate to comment further.”
An air ambulance was seen leaving the area.
Live firing was scheduled to take place at the range from Monday to Friday.
Castlemartin is the only UK Army range normally available for direct-fire live gunnery exercises and is used by Army, Army reserves and cadets.
It is also used by civilian organisations and research establishments.
The range, opened by the War Office in 1938, covers 5,900 acres on the south Pembrokeshire coast.