An unarmed North Korean soldier crossed the inter-Korean border Thursday to defect to South Korea, the military said.

According to the Joint Chiefs of Staff, the soldier crossed the military demarcation line around 10 a.m. No clash occurred in the process.

“The military has the defector in custody and is conducting an investigation into why and how he defected,” the JCS said. The military is reportedly planning to conduct joint questioning on the soldier with related organizations, including the National Intelligence Service.

No particular movement by the North Korean military was observed around the time of his defection, according to the JSC.

It marks the first defection of a North Korean soldier defecting across the MDL since June of 2015.

Last year’s data by the Defense Ministry shows that a total of 65 North Koreans had defected from 2010 to July, 2015 by crossing the MDL or the Northern Limit Line.

A total of 59 had used the sea route four crossed the border on land while the other two had defected via Inter-Korean Transit Office in Paju, Gyeonggi Province.

The number of defections by border crossing peaked in 2011 at 39, but declined to five, one, six and four in the subsequent four years. Only one had defected in such route this year before Thursday.

But the overall number of defectors from January to July marked an on-year increase from 705 to 815, according to the Unification Ministry.

There have also been several high-profile defections recently, including the August defection of former London-based diplomat Thae Yong-ho.

South Korean government has attributed the increase in defection mostly to the UN-led economic sanctions and disdain toward Kim Jong-un regime.

By Yoon Min-sik (minsikyoon@heraldcorp.com)