A North Korean official denounced a report by South Korea's spy agency that leader Kim Jong Un had ordered the execution of 15 senior officials as "malicious slander" but acknowledged that executions took place.

South Korea's National Intelligence Service told a parliamentary committee last week that Kim had ordered the 15 officials, including the vice forestry minister, to be executed for challenging his authority, and said Kim used fear and intimidation to rule the country.

"Malicious slander," Pak Yong Chol, a deputy director for the North's Institute for Research into National Reunification, said when asked by CNN about the South Korean spy agency's report on the executions.

"Especially as they try to link the allegations against to the august name of our Supreme Leader Marshall Kim Jong Un," Pak said, according to CNN's website.

He acknowledged that executions of those who try to overthrow or subvert the government took place. "It is very normal for any country to go after hostile elements and punish them and execute them," he said in the interview.

In 2013, Kim, who is believed to be in his early 30s, purged and executed his uncle, Jang Song Thaek, once considered the second most powerful man in the North, for corruption and crimes against the state.

North Korea, heavily sanctioned by the United Nations for its missile and nuclear tests, is technically still at war with the South after the 1950-53 Korean War ended in a truce, not a peace treaty.