"It is with deep sadness that I can confirm the death of a soldier from the Royal Tank Regiment who died as a result of injuries sustained in an incident at Castlemartin Ranges," veterans minister Tobias Ellwood said in a statement released by the defence ministry.
Three other soldiers were injured in the incident in southwest Wales yesterday, Ellwood said, without giving further details.
"The safety of our personnel is our absolute priority and a full investigation is underway to understand the details of this tragic incident," he said.
A 2013 inquest into Maguire's death found that he had been unlawfully killed.