The leaflets criticize South Korean President Park Geun-hye and her administration's decision to resume anti-North propaganda broadcasts through loudspeakers along the border.

The Korea Composite Stock Price Index (KOSPI) closed down 2.3 percent at 1,845.45 points, after retreating as much as 3.2 percent.

"I think the General (Kim Jong Un) likely took note of this some 10 years of experience in operations regarding the South plus his background in inter-Korean talks when considering him as Kim Yang Gong's successor", he added.

Mr Lee said the pamphlets that prompted him to escape in 1990 explained that the regime in Pyongyang had lied in teaching that South Korea provoked the Korean War. North Korea responded by restarting its own border broadcasts and floating the balloons over the border carrying anti-South leaflets Seoul officials said.

An analyst from a state-run think tank, who asked not to be named, said it is "not usual" to have someone with a military background lead South Korea-related operations within the Party, but there has been precedent in the 1960s.

North Korea goes to all lengths to defend the cult of personality around the Kim family and project absolute control.

U.S. Deputy Secretary of State Antony Blinken on Wednesday called for China to play "a special role" in strengthening sanctions against North Korea to punish it for its latest nuclear test in violation of U.N. Security Council resolutions.

During a meeting with South Korean Foreign Minister Yun Byung-se, Blinken said Seoul and Washington are working closely in NY with the United Nations Security Council.

Another leaflet dropped on the South had a cartoon of Ms Park in a red bikini being thrown into a rubbish bin as "human filth".

Following the meeting, Blinken told reporters that China shares commitment and conviction in North Korea's denuclearization. It is not the first time North Korea has lashed out at Park, the South's first female president, in a sexist or derogatory manner. "We are looking to China to show leadership on this issue".

The so-called Hermit Kingdom is also reportedly taking steps to further isolate its citizens by blocking cellphone signals along the Chinese border and increasing patrols to catch would-be defectors.

They are quintessentially North Korean, the sort of language you see in their media and propaganda, right down to details like the colours and quality of paper used.