A South Korean official says a North Korean soldier has defected to the South after killing two officers.

A South Korean Defense Ministry official says the defection took place around noon on Saturday across the western section of the heavily fortified Demilitarized Zone separating the two countries. The South Korean military says the soldier used a loudspeaker to inform the South Koreans of his intention to defect.

The official said the soldier is being interrogated and has confessed to shooting two of his superior officers before crossing the border.

Defections across the DMZ are rare because the border is tightly sealed and both sides are heavily armed.

The senior analyst in Seoul for the International Crisis Group, Daniel Pinkston, says defections across the DMZ are rare. The border is tightly sealed and heavily armed, and the personnel staffing the area are hand-picked.

“Those who are stationed in the border area, around the DMZ and especially right on the DMZ, are those who are considered to be loyal to the regime. They've been screened and they do not put people there who would be considered disloyal.”

The last known incidence of a North Korean soldier defecting across the DMZ was in 2010.

Under North Korea's collective punishment system, an act of this magnitude would mean harsh treatment for the soldier's family, extending for three generations.

More than 23,500 North Koreans have escaped and resettled in South Korea since the Korean War ended in 1953 with a cease-fire agreement. But nearly all of them make their way through China and Southeast Asia to get to South Korea, risking repatriation if they are caught in China.