/ Updated 
By Reuters

A North Korean soldier defected to South Korea on Thursday, the South's military said, making a rare crossing of one of the world's most heavily fortified borders amid heightened tension between the rival neighbors.

The soldier crossed the military demarcation line that runs through the demilitarized zone (DMZ) dividing the two Koreas, which remain in a technical state of war since their 1950-53 conflict ended in a truce, not a peace treaty.

South Korea and US soldiers stand guard during a ceremony marking the 63rd anniversary of the signing of the Korean War ceasefire armistice agreement at the truce village of Panmunjom, along the Demilitarized Zone (DMZ) on July 27, 2016. The armistice agreement on July 27, 1953 brought three years of active combat in the Korean War to a halt, but the two Koreas are still technically at war as no formal peace treaty was signed.KIM HONG-JI / AFP - Getty Images

While on average more than 1,000 North Koreans defect to South Korea every year, most travel via China and it is unusual for a North Korean to cross the DMZ, which is heavily mined and lined with barbed wire and soldiers on both sides.

The last such crossing was in June 2015.

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The soldier was unarmed and there was no exchange of fire, a South Korean military official said.

He walked across an eastern part of the front line at around 10 a.m. local time and was being questioned over how and why he made the crossing, South Korea's Office of Joint Chiefs of Staff said in a statement.

The escape follows a series of high profile defections that have angered North Korea at a time of heightened international tension over its nuclear and missile tests.

File footage showing Thae Yong Ho speaking on a podium in London.REUTERS TV / Reuters

The most prominent defector was Thae Yong Ho, the North's deputy ambassador to Britain, who became the highest-ranking diplomat to defect to the South when he arrived last month, an embarrassing blow to the government of North Korean leader Kim Jong Un.

In April, 12 North Korean waitresses in a restaurant in China fled to the south, along with their manager.

Tension has been high on the Korean peninsula since the 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.

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That drew widespread condemnation, prompting global powers to seek toughened sanctions against the isolated country.

Separately, media reported that a North Korean teenager who took part in a Hong Kong maths contest in July and later sought asylum at the South Korean consulate there had arrived in South Korea.

South Korea declined to confirm or comment on the report.

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