A Korean Marine has hanged himself in his barracks, an official said Monday, in a new blow to the Corps after a corporal who claimed he was bullied went on a deadly shooting spree last week.

The 19-year-old Private First Class, identified only as Jung, was found by colleagues Sunday night hanging in a barracks shower room in the southeastern port of Pohang, a Marine Corps spokesman said.

Military investigators found an apparent suicide note in his locker with complaints about his life and a message for his parents.

"Investigations are under way to determine the reason for the suicide and if there was any harsh treatment (of Jung)," the spokesman told AFP.

The defence ministry vowed a crackdown on bullying throughout the 650,000-strong largely conscript military.

The elite Marine Corps is reeling from a storm of criticism following the July 4 shooting rampage by a Marine corporal who complained of bullying and beatings by superiors.

The shooting at a barracks on Ganghwa island, west of Seoul and near the tense sea border with North Korea, left four soldiers dead and one injured. The corporal surnamed Kim was also injured by a grenade blast in a suicide attempt.

An army psychology test had earlier found Kim to be unstable and to have difficulty in coping with military life, military investigators have said, and he had been drinking before the shooting.

A Marine private arrested for allegedly assisting Kim's rampage also claimed to have been bullied but denied involvement in the actual shooting.

The private told investigators a superior had burned his Bible and set his uniform on fire, media reports said.

A colonel and a lieutenant-colonel from the Ganghwa unit will be sacked as commanders as a punishment. Some of the soldiers allegedly involved in bullying the pair may be arrested, said defence ministry spokeman Kim Min-Seok.

The military has vowed to make "utmost efforts" to end bullying in barracks following an emergency order from Defence Minister Kim Kwan-Jin.

The Marine Corps is responsible for guarding frontline islands in the Yellow Sea near the disputed border with the North.

But last week's incident -- the third to afflict the military overall in six years -- raised questions about standards of discipline in the armed forces. (AFP)