The court said Kim had to pay for the suffering he caused

Kim Dong-min threw a grenade inside his barracks near the border with North Korea, and then opened fire at random at colleagues they slept.

Kim, 22, had complained of bullying by his fellow soldiers.

An inquiry into the incident found Kim had become so obsessed by computer war games that he could no longer tell the difference between fantasy and reality.

In a ruling quoted by Yonhap news agency, the 3rd Army's district court said: "We can't help separating the accused from society permanently, though we take into account his lack of a previous criminal record, his youth and unease at being in a closed place.

"The victims, bereaved families and surviving soldiers have suffered deep despair and unforgettable damage," it said.

According to one account, the attack was so ferocious that witnesses feared South Korea was being invaded.

Kim's defence lawyer said he would appeal the ruling at a higher court.

The conscript was a university student before beginning his two years of military service last December.

The BBC's Charles Scanlon says there are frequent reports of bullying and violence against conscripts in South Korea's 600,000-man army.