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(CNN) - It's "very likely" that North Korean leader Kim Jong Un's powerful uncle, Jang Sung-taek, has been removed from his top-level position in government, two South Korean lawmakers said Tuesday, citing a briefing from their county's intelligence service.
And two close allies of Jang have been publicly executed, one of the South Korean lawmakers said at a news conference.
"Jang Sung-taek has not been seen now for a couple of months, maybe more when it comes to actually standing next to Kim Jong Un," said former Ambassador to South Korea Christopher Hill, who currently serves as dean of the Josef Korbel School of International Studies at the University of Denver.
CNN has not been able to independently confirm the report. But while the trustworthiness of South Korean intelligence on North Korea "varies," Hill says in this case it has "a greater probability of being true."
Jang has had problems in the past, and this would not be the first time that he has been purged, said Hill, who led the U.S. delegation during the six-party talks with North Korea from 2005-2009.
At the beginning of Kim Jung Un's rule, Jang's constant appearance at the new leader's side "opened up a question whether Kim Jong Un was really in charge," said Hill.
"And one thing we know about this boy king is that he very much wants to show he's in charge," said Hill.
Speaking to motivations for the reported purge, Hill said Kim Jung Un may have had a falling out with his uncle, as his father and successor Kim Jong Il had at various times.
"(Kim Jung Un) is also always at pains to show he's a different kind of guy from his father," said Hill. "He's also the kind of guy who makes these kind of impetus decisions. And certainly last spring, when he was threatening war on the rest of the planet, you didn't see much of Jang Sung-taek involved in that."
In other words, Jang was a moderating force in the North Korean government.
"There are indications that he was sort of more aware of market forces in economics than maybe Kim Jong Un was. There certainly has always been the view that Jang Song-taek, you know, erred on the side of being more moderate than the rest of the leadership," said Hill.
"That said, he's obviously a pretty hard-nosed guy who's been very much a part of that miserable leadership for many, many years," said the former ambassador.
Given the closely guarded nature of the Hermit Kingdom, it is difficult to predict what Jang's purge really means.
"I have a feeling it doesn't mean anything good, and could in fact mean that Kim Jong Un is very much on his own, along with some of these new military people that he has appointed himself," said Hill.
Two Americans are currently being held by North Korea. Businessman and Korean War veteran Merrill Newman, 85, has been detained for more than 30 days, says his family. Newman apologized for his actions, including for killing troops and civilians during the Korean War, North Korea's state-run news agency reported Saturday. Also imprisoned is Kenneth Bae, an American citizen arrested in November of last year and sentenced in May to 15 years of hard labor. The North Korean regime says he was found guilty of "hostile acts" and attempts to topple the government.
Getting Americans released in countries such as North Korea is a "painstaking process," says Hill.
"Rule number one is not to talk about it too much in public, except to state the obvious, that they ought to be released immediately," said Hill. "I am sure, I have no doubt that the U.S. government is doing what it can to get these people released. But the more they talk about it publicly, probably the more difficult it is."
"What these issues often descend to is the internal politics of the country in which they're being held captive. And so the more we say publicly, the more that could be used by whichever side," said Hill. "It's important to work quietly behind the scenes. And I suspect we're doing that. And I do hope the Chinese are stepping up in this regard."
China is North Korea's leading ally.