A South Korean Marine has opened fire on colleagues at a frontline guard post, killing three of them and injuring two.

A South Korean Marine opened fire on colleagues at a frontline guard post today, killing three of them and injuring two, the defence ministry said.

The corporal was on duty at Ganghwa island west of Seoul, a ministry spokesman said, adding the incident only involved South Korean forces. He had no other immediate details.

A staff sergeant, a corporal and a lance corporal were killed while a corporal and a private were injured, Yonhap news agency quoted an unidentified military official as saying.

The shooter himself was also slightly injured, the official said, adding that the wounded received first aid and were taken to hospital.

Similar incidents have been reported in the past among the South’s 650,000-strong military.

Eight soldiers were killed and two seriously injured in 2005 when a soldier threw a grenade and sprayed bullets over sleeping colleagues at a frontline guard post north of Seoul.

The soldier in the 2005 incident alleged senior colleagues had bullied him.

In 2008 an army private struggling to adapt to military life tossed a grenade at sleeping colleagues, injuring five.

Most South Korean men must undergo at least two years of military service.

North and South Korea are still technically at war after their 1950-1953 conflict ended in an armistice instead of a full peace treaty.

The military has campaigned against abuse and harassment of junior soldiers by their seniors.