By Mark Stone, Asia Correspondent
South Korea's spy agency has revealed details of what it believes were the reasons behind the 40-day disappearance of North Korean leader Kim Jong-Un.
In a closed-door hearing, officials from South Korea's National Intelligence Service (NIS) told parliamentarians he was suffering from Tarsal Tunnel Syndrome, which is the compression of the tibial nerve in the foot.
In Mr Kim's case, the compression is understood to have been caused by a cyst in his right ankle - said to be the result of obesity, smoking and his busy work schedule.
The intelligence agency officials claimed Mr Kim had been operated on by European doctors in September or October.
Handout photo of Mr Kim visiting a baby home and orphanage
The spy officials also claimed that about 200 military officers had been demoted for "underperformance" and 50 executions had been carried out in North Korea so far this year, including officials associated with Mr Kim's executed uncle Jang Song-Thaek.
Discussing North Korea's widely-condemned labour camps, the officials said that intelligence suggested they were growing in size.
Video: Inside North Korea: Full Programme
The revelations come as North Korean officials at the United Nations hinted they could allow a UN human rights inspector into the country.
At an unprecedented meeting in New York, North Korean diplomats met Marzuki Darusman, a UN special investigator on human rights.
Following discussions, the North Korean delegation told the AP news agency that they "envisaged" a visit by Mr Darusman to the country.
In theory, the visit could represent a breakthrough in international efforts to establish, first-hand, the reality of human rights abuses in North Korea.
Video: The Defectors: A Special Programme
However, reports from South Korea suggest the North is secretly moving inmates out of one its prison camps.
According to South Korea's Chosun Ilbo newspaper, prisoners at Yodok camp are being moved in "apparent preparation for a PR exercise showing conditions are not as bad as reported".
In February, a UN Commission of Inquiry published testimonies from North Koreans who have escaped the country.
The report was the culmination of public hearings with more than 80 victims in Seoul, Tokyo, London and Washington. It outlined a litany of crimes including murder, enslavement, torture, imprisonment and rape amounting to "crimes against humanity".
Video: Feb: Surviving N Korea Prison Camps
However, the report authors, led by retired Australian judge Michael Kirby, were refused access to North Korea itself. Officials there have repeatedly dismissed its findings as "fabrications" and described the witnesses as "human scum".
The Chosun Ilbo newspaper is also suggesting North Korea might now try to improve the appearance of one of its camps.
"The regime is transferring the inmates one by one during the night so that their movement can't be detected by satellites," the newspaper quoted a source as saying.
The UN Commission of Inquiry called for North Korea to be referred to the International Criminal Court, a procedure which must be actioned by the UN Security Council.
Video: Truth Of Gulags Could Remain Hidden
However, North Korea's closest ally, China, holds a permanent seat on the council and has the power of veto, making any ICC referral unlikely.
:: In a separate development, Japanese and North Korean officials have begun two days of talks in Pyongyang about the abduction of Japanese citizens in the 1970s and 80s.
The issue has long been a major obstacle in relations between the two nations, and the talks are the first in the capital in 10 years.
