About a thousand North Koreans defect to South Korea every year, usually through China.

But on Thursday an unidentified North Korean soldier took a dangerous shortcut through heavily mined territory bound with razor-sharp concertina wire, with tens of thousands of armed soldiers on both sides.

South Korea's Joint Chiefs of Staff said the man managed to cross unscathed at about 10 a.m. (0100 UTC) without a shot fired by either side. "He is now being held in custody for questioning," the JCS said.

The last time a soldier was able to defect over the four-kilometer (2.5-mile)-wide DMZ was last year when a teenage North Korean soldier surrendered himself to South Korean border guards at Hwacheon, northeast of Seoul.

Tension has been boiling on the Korean peninsula since the communist North conducted its fourth nuclear test at the beginning of the year and followed it with an unprecedented string of missile tests, and then its fifth and largest nuclear test this month.

The Koreas have shared the world's most heavily fortified border since the end of the 1950-53 Korean War. The conflict ended with a ceasefire - not a peace treaty - leaving the Korean Peninsula in a technical state of war that occasionally boils over in exchanges of live fire.

More than 29,000 North Koreans have defected to capitalist South Korea since the end of the truce. The most prominent defector was Thae Yong Ho, the North's deputy ambassador to the United Kingdom, who became the highest-ranking diplomat to defect when he arrived last month in Seoul.

North Korea has branded defactors as disloyal "human scum."

jar/es (AP, AFP, Reuters)