A bloody purge in North Korea following the sudden death of leader Kim Jong-il late last year saw barbaric methods including mortar rounds used to execute high-ranking military officials, a South Korean government source said Wednesday.

"When Kim Jong-un became North Korean leader following the mourning period for his father in late December, high-ranking military officers started disappearing," the source said. "From information compiled over the last month, we have concluded that dozens of military officers were purged." The source added Kim Jong-un ordered loyal officials to "get rid of" anyone caught misbehaving during the mourning period for Kim Jong-il.

But contrary to reports that an assistant chief of the Ministry of the People's Armed Forces was put in front of a firing squad for being drunk during the mourning period, he was executed using a mortar round in line with Kim's orders to leave "no trace of him behind, down to his hair."

The source said the official was placed on the spot where the round would hit, and the grisly execution obliterated him.

Besides the assistant chief and an assistant chief of the General Staff Department, frontline commanders were also executed, the source said.

Kim Jong-il also purged dissenters after the death of his father Kim Il-sung in 1994. Even those caught for minor infractions were executed by a firing squad.

But Kim Jong-un's methods appear even more brutal. A source familiar with Nor th Korea said, "It appears that the loyalty pledged by the military did not satisfy the young leader, who is sensitive about his age." Kim junior is 28 or 29.

The source said the drastic measures may have been proposed by Kim's confidant Kim Jong-gak (62), the first deputy director of the General Political Bureau of the North Korean People's Army.