A top South Korean official said his country remains confident that there have been no unusual developments in North Korea, suggesting that rumors about the health of leader Kim Jong Un are untrue.

Unification Minister Kim Yeon-chul told a closed-door Seoul forum on Sunday that South Korea has enough intelligence to confidently say that there are no unusual developments in North Korea that back up speculation about Kim Jong Un's health, according to his ministry.

The minister said he would not reveal what specific intelligence led to that conclusion, but stressed that it had undergone a complex analysis process.

The rumours about Kim's health began to swirl after he missed the April 15 commemoration of the 108th birthday of his grandfather, North Korea founder Kim Il Sung.

Kim Jong Un is the third generation of his family to rule North Korea, and he hadn't missed the event, one of the most important in the North, since assuming power after his father Kim Jong Il's death in late 2011.

The unification minister's comments are a reiteration of previous South Korean statements maintaining that Kim Jong Un appeared to be handling state affairs normally and that no unusual activities had been detected in the North.

Those earlier comments failed to dispel the rumours about Kim, which have been fed by the silence of North Korea's state media about their leader's whereabouts.

As the absolute leader of country with a nuclear weapons programme, Kim's health is matter of intense interest both regionally and globally. If something were to happen to Kim, some experts have said it could lead to instability in North Korea.

South Korea's presidential office earlier said that it has information that Kim has been staying out of Pyongyang and that there had been no emergency readiness order issued by the North's military or the ruling Workers' Party that likely would have been made if Kim were truly in bad condition.

Recent satellite photos released Saturday by 38 North, a website specialising in North Korea studies, showed that a train likely belonging to Kim has been parked at his compound on the country's east coast since last week.

The train's presence does not prove the whereabouts of the North Korean leader or indicate anything about his health, but it does lend weight to reports that Kim is staying at an elite area on the country's eastern coast, 38 North said.