North Korea is purging officials who had been close to Jang Song-thaek, the once-powerful uncle of leader Kim Jong-un who was executed this month, a South Korean minister said on Monday.

Jang, once the North’s unofficial number two and Kim’s political mentor, was executed on December 12 on a array of charges including treason and corruption.

The shock purge — staged in an unusually dramatic and public fashion in the isolated communist state — was the biggest political upheaval since the young ruler took power after the death of his father and the former leader, Kim Jong-il, two years ago.

Seoul’s spy chief earlier this month said two of Jang’s associates had also been executed, while Pyongyang reportedly recalled some diplomats or trade officials overseas who were believed to have been close to Jang.

“We are seeing signs that those who were deeply involved with Jang are being recalled and purged,” Ryoo Kihl-jae, South Korea’s unification minister in charge of cross-border affairs, told lawmakers.

The purge however appears to be targeting a relatively small circle of officials, Ryoo said, rejecting speculation of a sweeping clear-out of party and military ranks.

“We do not see that it [the purge] is being carried out on a large scale, though it still needs to be seen to what direction it would develop,” he told members of parliament’s foreign affairs committee.

Yonhap news agency said Saturday the North’s ambassador to Sweden, Pak Kwang-chol, and his wife had been summoned back to Pyongyang.

Pak, who had taken the post in Sweden in late 2012, was seen at Beijing airport being escorted by North Korean officials before taking the flight to Pyongyang on Saturday, it said, quoting a diplomatic source in China.

Yonhap said earlier this month that Jang’s nephew and the North’s ambassador to Malaysia, Jang Yong-chol, had also been recalled.

The execution of Jang raised questions about political instability in the impoverished but nuclear-armed North.

Jang is believed to have played a key role in cementing the leadership of Jong-un. But the 67-year-old’s growing political power and influence was increasingly resented by the young leader barely half his age, analysts say.

The Kim family has ruled the North for more than six decades through an iron fist and a pervasive personality cult. Those showing the slightest sign of dissent have been sent to prison camps or executed.