South Korea's spy agency chief on Monday denied as "totally untrue" persisting news reports that close aides to the executed uncle of North Korean leader Kim Jong-un have fled the communist nation and sought asylum in China, lawmakers said.

National Intelligence Service Director Nam Jae-joon also reported to a parliamentary intelligence committee that North Korea has beefed up artillery units and exercises, and could attempt provocations against the South between January and March, the lawmakers said.

The agency also believes that Pyongyang is ready to conduct its fourth nuclear test at any time, though that does not mean a test is imminent, said Rep. Cho Won-jin of the ruling Saenuri Party and Rep. Jung Chung-rai of the main opposition Democratic Party in a joint briefing following the committee meeting.

Since North Korea's execution of the leader's uncle, Jang Song-thaek, some South Korean media outlets have reported that close associates to him have fled the bloody purge campaign, sought asylum in China, and are under the protection of South Korean authorities.

The NIS chief "reported that (the reports) are totally untrue," Rep. Chung said.

The agency also reported that it believes the North's young leader has no problem with his grip on power, and that Jang was believed to have been executed mainly because of his involvement in business rights for lucrative projects, one of them a coal related project, according to the lawmakers.

"In a situation where disputes over business rights between agencies and the issue of Jang's aides overstepping their authority have built up, Kim Jong-un must have ordered the disputes be sorted out," Rep. Chung said. "When the order was not complied with,

(Jang) was executed for violating the supreme leadership. That's the NIS analysis."

"On the surface, Kim Jong-un's grip on power is believed to have no big problems because Jang's execution did not stem from an internal power struggle," Chung said, citing the NIS briefing.

The agency also reported that Jang's wife, Kim Kyong-hui, is believed to be safe, the lawmakers said. Kim Kyong-hui's fate has been in question after she failed to show up to a national memorial service for late North Korean leader Kim Jong-il. (Yonhap News)