Kim Jong-un falls off the radar as North and South Korea agree to talk

There are feverish rumours of illness, even talk of a coup, as secretive state's leader vanishes from the public eye

The 31-year-old's walk was somewhere between a limp and a waddle. The speculation was feverish: Kim Jong-un was ill, he was addicted to Swiss cheese, he had gout, he had disappeared – was he still alive?

The question still remains – Kim has not been seen in public for a month – but yesterday, among the many sober suits at the Asian Games in Incheon, South Korea, appeared a Vice Marshal of the Korean People's Army, the North's second most powerful person. Wearing an olive uniform, Hwang Pyong-so had arrived.

In a flurry of diplomacy from the normally undiplomatic Pyonyang, Hwang's delegation also included another senior aide to Kim, Choe Ryong-hae, and Kim Yang-gon, a senior official of the ruling Workers' Party and a long-time veteran of dealings with the South.

That Kim is a sports enthusiast – he is understood to enjoy basketball and football – is well documented, but the real purpose of the delegation's visit soon became clearer. The North has agreed to resume talks, stalled since February, between senior officials either later this month or in November, according to officials from South Korea.

One analyst called it a "golden opportunity" for South Korean President Park Geun-hye to test North Korea's willingness, at the highest levels, to improve shaky ties. The past 12 months had seen a steady stream of insults traded between the divided neighbours and an unusual number of North Korean missile and rocket tests.

The delegation had a closed-door lunch meeting with South Korean Unification Minister Ryoo Kihl-jae and national security director Kim Kwan-jin. It was described by John Delury, an Asia specialist at Seoul's Yonsei University, as "a very high-octane group". He added: "Historically, North-South breakthroughs start from the top down, and if Park is serious that she wants to improve relations and jumpstart the reunification process, this is a golden opportunity."

The last such senior visit south was in 2009, when high-ranking Workers' Party official Kim Ki-nam and spy chief Kim Yang-gon, another official who visited the South yesterday, came to pay their respects to the late liberal South Korean President Kim Dae-jung.

Hwang is reported to still be first deputy director for military affairs in the Organisation and Guidance Department (OGD), a secretive group that used to report directly to Kim Jong-il, Kim Jong-un's father, who died in 2011.

On Friday, Vice News reported that Jang Jin-sung, formerly a key member of Kim Jong-il's propaganda machine, counter-intelligence official and personal poet laureate, had claimed that North Korea was "in the midst of a civil war" in September.

Jang, a defector, was reported to have said members of the OGD had stopped taking orders from the younger Kim. The OGD, Jang said, had effectively taken control of the country, with some seeking to gain wealth through increased foreign trade and open markets. "It's not actually consciously civil war, but there are these two incompatible forces at play," he reportedly said.

The alleged coup is said to have begun last year with Kim Jong-un only serving as a puppet leader while officials from the OGD, including Hwang, pulled the strings. It was, Jang claimed, triggered by the execution in December of Jang Sung-taek, Kim's uncle by marriage, who was a political rival of the OGD.

News of Jang Sung-taek's execution was accompanied by a string of extraordinary insults, branding him a "traitor for all ages" and "despicable human scum" who was "worse than a dog". A 2,700-word state-media report of his trial in a special military tribunal said he had admitted to plotting insurrection and a string of other crimes.

"By Jang dying, Kim Jong-un is now surrounded by the OGD," said Jang Jin-sung of the purge of Kim's uncle.

According to New Focus International, a news website that says it is informed by North Korean "exiles from many levels of society", the OGD has exercised virtual control over North Korea since the department's foundation in the early 1990s.

Last week, it reported on the promotion of Hwang to vice-chairman of the National Defence Commission. "But Hwang's recent promotion, even to a position in a [commission] considered by observers to be a powerful military institution, is not an indicator of rising power so much as existing clout becoming apparent to external light," the website reported.

"Hwang Pyong-so is first deputy director for military affairs in the OGD, whose figures exercised their powers and influence from behind the scenes, deliberately avoiding public and prominent posts."

Jang Jin-sung told CNN this weekend: "The power holders in North Korea are the OGD. They are calling the shots and not the words of one man they do not know. Basically, they are no longer loyal to the ruling king's word."