Eight cows were killed at an army training base after wandering into the line of fire.
A further four cows were injured during the incident at the Castlemartin range in Pembrokeshire on Friday.
The cattle moved into the range area after an inspection took place before the exercise began, according to the Ministry of Defence.
An MoD spokesman said: “Much of Castlemartin Training Area is grazed by cows and sheep.
“On July 10 some cattle moved in to the firing area after it was confirmed to be clear, but before firing started.
“They could not be seen by the unit training and unfortunately a number of cows were shot and killed or injured.
“Their presence was noticed by the range conducting officer who immediately halted the exercise.
“The farmer has been informed and made aware of his rights.”
Like many MoD training areas, parts of Castlemartin are leased to tenant farmer.
The ranges are inspected for livestock before each firing exercise.
The Defence Accident Investigation Branch has been informed and a serious incident report is being prepared.
A spokesman added: “In due course this will form part of a lessons learned exercise”.
The incident is the latest in a series at Castlemartin.
In 2017, two soldiers were killed during a tank explosion during a live firing exercise.
A subsequent investigation revealed a seal stopping explosive gases escaping into a tank crew’s turret was not in place before a lethal blast that killed Royal Tank Regiment corporals Matthew Hatfield, 27, and Darren Neilson, 31.
And two years ago, army captain Jonathan Price was jailed for 18 months and dismissed from the army for the gross negligence manslaughter of Ranger Michael Maguie at Castlemartin. The 21-year-old was hit by a stray bullet at the base in 2012.
