A top North Korean military official, thought to be behind the North's deadly attacks on South Korea in 2010, is sure to have replaced Kim Yang-gon, who died in a car accident in December, sources said Wednesday.

Gen. Kim Yong-chol, 70, who leads the North's reconnaissance bureau, has been recently appointed as the party secretary handling inter-Korean affairs, also doubling as the head of the United Front Department at the ruling party, the sources said.

"It is certain that Gen. Kim has replaced the dead official," said a source familiar to North Korean affairs. "He assumed the posts of the head of the UFD as well as party secretary."

If confirmed, it is a rare case that a North Korean military official has become a secretary of the Workers' Party of Korea.

Gen. Kim, known as a hardliner, is believed to have orchestrated Pyongyang's two deadly attacks on the South in 2010 -- the sinking of the Cheonan warship and the shelling of Yeonpyeong Island. The two attacks killed a total of 50 South Koreans, including two civilians.

He is also known for having masterminded the planting of land mines across the inter-Korean border that severely injured two South Korean staff sergeants in August last year.

Since 2009, Kim has led the North's Reconnaissance General Bureau tasked with intelligence operations in foreign countries and cyberwarfare. The bureau is known to be behind Pyongyang's alleged cyberattack on Sony Pictures Entertainment in 2014.

"If Gen. Kim is confirmed to have been appointed as a party secretary on inter-Korean affairs, there is the high possibility that he would not serve as the head of the North's Reconnaissance General Bureau any longer," another source said.

The Unification Ministry declined to confirm Kim's nomination.

"It is too premature to verify it," Jeong Joon-hee, a ministry spokesman, told a regular press briefing.

Kim's nomination may cast clouds over the already strained inter-Korean ties, which have dropped to one of the worst levels as a result of the North's fourth nuclear test on Jan. 6.

Kim Yang-gon, known for a dialogue-seeking figure, was called "the closest comrade-in-arms" of North Korean leader Kim Jong-un.

Kim, who served as the head of the United Front Department in the party, was part of the North's delegation to rare inter-Korean high-level talks in August following heightened tensions sparked by the land mine blast.

The two Koreas reached a rare deal on Aug. 25 to defuse military tensions and make efforts to promote inter-Korean civilian exchanges. (Yonhap)