Just two months after North Korea’s leader Kim Jong-un had his uncle Jang Sung-taek, a top official in the secretive communist regime, executed for treason, South Korean media report that Choe Ryong-hae, the ruling party’s military chief, has been arrested.

Choe is the vice chairman of the Central Military Commission that Kim leads and was believed to be one of this closest advisors. He is also one of the few members of the executive body of the Workers’ Party Politburo which previously included Jang. If Choe is removed, this presidium would only count Choe Yong-rim and Kim Yong-nam, both octogenarian figureheads, besides Kim Jong-un himself.

The news of Choe’s arrest was first reported on Friday by Free North Korea Radio, which is run by defectors in the South. One of its sources speculated that Choe had been arrested for failing to instill sufficient loyalty in the army ranks.

Kim has tightened his grip on power since taking over from his father, Kim Jong-il, in late 2011. In July 2012, he relieved the army chief of staff, Vice Marshal Ri Yong-ho, of his post. Observers of the North Korean regime believed Ri had originally been appointed by Kim Jong-il to shield his son from a potential challenge by the generals. Ri had also served as vice chairman of the Central Military Commission.

Choe, a party apparatchik with no military experience, took over the role from Ri and was promoted to vice marshal, signaling that the balance of power in Pyongyang had shifted to the party.

Following Ri’s purge, South Korean media reported that as many as two hundred army officers might have been removed from office since Kim took power, supporting the thesis that the young despot was moving away from his father’s “military first” doctrine.

Choe’s arrest, if corroborated, would therefore come as something of a surprise, even if North Korean state media started referring to him as a “general” as early as December 2012, suggesting he had been demoted.

Late last month, South Korea’s Chosun Ilbo newspaper also reported that Choe was fading from public view, appearing by Kim’s side less and less which usually indicates that a North Korean official has fallen out of the ruler’s favor.

For Choe, it would not be the first time. In 1997, he was removed as head of the Kim Il-sung Socialist Youth League — officially due to illness but reportedly because he had been found stripping assets.

South Korea’s Ministry of Unification said on Monday it could not confirm the rumor of Choe’s arrest.