South Korean soldiers fire warning shots at border guards from North Korea who appeared to be searching for the soldier.

A North Korean soldier has defected to South Korea by crossing the demilitarised zone (DMZ) under the cover of thick fog, officials in Seoul say.

South Korean soldiers later fired about 20 warning shots at border guards from North Korea who appeared to be searching for the defected soldier, the officials said.

It was the fourth defection of a North Korean soldier this year.

Speaking to Al Jazeera from Seoul, Se-Woong Koo, a political analyst and publisher of Korea Expose, a news magazine, said North Korea’s economic situation is prompting soldiers and citizens to risk their lives by leaving the country.

“There have been 15 cases in which North Koreans crossed the DMZ or through the East China Sea by ships in the last year or so, Se-Woong said.

“South Koreans react to this with surprise and alarm. But then again, we have seen other cases before, including last year and the year before that,” he added.

On November 13, a North Korean soldier defected along the Joint Security Area (JSA) that is policed by both the South and North’s militaries, with soldiers staring each other down face-to-face at the heavily fortified border that divides the Koreas.

Gunfire rang out and South Korean troops found the bleeding North Korean soldier – dressed in a combat uniform but unarmed – on their side. He was taken by helicopter to a nearby hospital for treatment.

The South Korean soldiers did not return fire.

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The Korea Joongang Daily reported the North Korean was shot in the shoulder and elbow.

Yonhap described the incident as “a very rare case” because North Korean troops stationed along the DMZ are known for their loyalty to Pyongyang.

“Last month was a dramatic moment because of the shots that were fired by North Korean soldiers at the defector, and because the South Korean soldiers had to cross into the zone to drag him to safety,” Se-Woong said.

South Korean statistics, however, showed an overall decrease of defections from North Korea by 20 percent in the first month of 2017 in comparison to the year before.

“Many in the South attribute the decrease to increased surveillance put in place under current North Korean leader Kim Jong-un along the main channel of defections, which is the border between North Korea and China, Se-Woong said.

“As a result the numbers have gone down there. At the same time we’ve seen a slight increase in the extraordinary defections through the DMZ,” he added.

“The fact that we are paying so much attention to these cases goes to show that we are struggling to find out what is going on in North Korea. There are simply not enough sources that give us information about the regime,” Se-Woong said.