South Korea's top Marine commander has offered to resign to take responsibility for the deadly shooting rampage by a marine in his barracks early this month, a military official said Thursday.

Marine Corps Chief of Staff Yoo Nak-joon submitted his resignation to Defense Minister Kim Kwan-jin on Tuesday, the official said on the condition of anonymity.

"Gen. Yoo conveyed his intention to resign at a meeting with Defense Minister Kim on Tuesday afternoon," the official said.

A 19-year-old marine corporal surnamed Kim opened fire on July

4 at his base on Ganghwa Island, the 2nd Marine Division, near the tense maritime border with North Korea, killing four fellow marines and injuring another.

Military investigators found that Kim, who was found to be mentally unstable at the time of the shooting, was angered by alleged bullying and beatings by his colleagues.

The defense ministry has ordered all military commanders to inspect the standards of discipline and irregularities amid concerns about discipline since the rampage.

The shooter was arrested after unsuccessfully trying to kill himself with a grenade. (Yonhap News)