Lieutenant Kenneth Sheehan was supervising the firing of an anti-tank, bazooka-type weapon at a military range in north Cork when he sustained serious injuries to his face, chest and right arm.
The junior officer, who is from Cork city, was supervising a routine training course when the accident happened.
He was standing close to the Bofors AT-4, a shoulder-launched weapon, when he was hit.
Lt Sheehan, who joined the Defence Forces in 2002, sustained the injuries at about 11.30pm on Wednesday at Lynch Camp, near Kilworth.
He was treated by army paramedics at the scene before being rushed by ambulance to Cork University Hospital.
He underwent emergency surgery at the hospital yesterday and his condition was described as critical but stable.
The officer is expected to require further surgery.
A Defence Forces spokesman said military police had launched an investigation and that all firing of the Swedish-made Bofors AT-4 had been suspended pending the outcome of that investigation.
The weapon has been used by the army since 1998 and has been fired thousands of time in training without incident.
“The Defence Forces fires weapons and rehearses military skills regularly by day and night so that soldiers are proficient in all conditions, at home and overseas. Such training exercises are subject to strict supervision and safety procedures. The investigation will examine these procedures,” the Defence Forces spokesman said.
Major General Pat O’Sullivan, deputy chief of staff of operations, visited Lt Sheehan’s family at CUH yesterday and offered them his support.
Defence Minister Willie O’Dea also spoke to them by telephone.
“This fine young man is in our thoughts and prayers.
“I want to take this opportunity to wish him and his family well in dealing with this accident and in recovering from his injuries,” Mr O’Dea said.
“I have been advised by the Chief of Staff that the accident scene has been preserved and a full investigation into the incident is taking place.”
Lt Sheehan is normally based at Collins Barracks, Cork, with 1st Field Communications and Information Services Company.
However, he was recently seconded to the Southern Brigade training centre as an instructor working with 38 army privates.
He served in Liberia with the 94 Infantry Battalion, UNMIL in 2005 and last year was in Chad with the 97 Infantry Battalion,.