Image copyright AP Image caption Defections across the North-South land border are rare 
 
 A North Korean soldier has defected to the South across the two countries' heavily armed border, South Korean officials have said. 
 
 The soldier said he shot dead two officers before crossing over just after noon (03:00 GMT) on Saturday. 
 
 Our correspondent says defections across the land border are rare. The last soldier fled in 2010. 
 
 More than 20,000 North Koreans have gone to the South in the last 60 years, mostly via China and SE Asia. 
 
 The two countries are still technically at war after the 1950-53 conflict, which ended in a ceasefire not a peace treaty. 
 
 Gunshots heard 
 
 The soldier was quoted as saying that he killed his platoon and squad commanders while on guard duty. 
 
 A defence ministry official said six gunshots were heard and guards saw the soldier cross the demarcation line on a western section of the tightly guarded border. 
 
 They used loudspeakers to establish that he wanted to defect and guide him to safety, they added. 
 
 The official said he was in protective custody and was still being interrogated. 
 
 There has been no confirmation of the North Korean casualties and no unusual activity observed on the North Korean side of the border. 
 
 The BBC's Lucy Williamson in Seoul says that about a million soldiers and a million land mines line the Demilitarised Zone, and only a handful of people have crossed from North to South by land in the past few years. 
 
 Most make their way to the South by a long and dangerous land route, she says. 
 
 This takes them through China and on to countries such as Thailand or Mongolia. ||||| In what is apparently the first such incident in nearly two-and-half years, a North Korean soldier has defected across the heavily armed land border with the South. 
 
 
 
 South Korean military officials say a soldier from the North claims he shot and killed his platoon and squad chiefs while on guard duty before defecting across the heavily fortified Demilitarized Zone. 
 
 
 
 The incident occurred at noon Saturday along the western section of the DMZ. 
 
 
 
 Officials say South Korean troops at the border heard gunshots, confirmed the North Korean soldier's desire to defect, and escorted him to a guard post. He is now undergoing interrogation. 
 
 
 
 The senior analyst in Seoul for the International Crisis Group, Daniel Pinkston, says there is no indication the defection denotes any instability in the reclusive and impoverished state. 
 
 
 
 “We'll see as he's debriefed and it's just a one-off incident, so I don't think there's too much we can read into it besides that at this point,” he said. 
 
 
 
 Pinkston points out that soldiers in North Korea's army posted to the border area are scrupulously vetted. 
 
 
 
 “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,” he said. 
 
 
 
 Defections by North Koreans along the DMZ are rare. The last known incident involving a soldier occurred in March, 2010. 
 
 
 
 Under North Korea's collective punishment system, a disloyal act of this magnitude would mean harsh treatment for the soldier's family, extending for three generations. 
 
 
 
 The Joint Chiefs of Staff in Seoul says South Korea has increased surveillance along the DMZ following the incident and the military has activated its crisis management facility. However, there is no sign of any unusual activity on the northern side. 
 
 
 
 The DMZ is a legacy of the 1953 armistice which brought a three-year civil war to a halt. But the two Koreas have never signed a peace treaty.
– A rarity in the demilitarized zone between North and South Korea today: A soldier from the North defected and claims to have killed two commanding officers in order to do so, reports the Voice of America. Soldiers in the South heard about six shots, then allowed the soldier to cross the DMZ. He is still being interrogated. “We'll see as he's debriefed and it's just a one-off incident, so I don't think there's too much we can read into it besides that at this point,” says an analyst with the International Crisis Group. Pyongyang, not surprisingly, has not confirmed the incident, reports the BBC. The North generally puts only its best soldiers at the border after a careful vetting process, and defections are rare. One reason: The family of a defecting soldier is sure to face harsh punishment, notes VOA.