They are looking for any sign, a smile perhaps, that could indicate Mr Kim Jong Il's state of health.

'We have dissected everything from Kim Jong Il's facial expression and body language, to voice analyses and background scenery to try to ascertain the state of his health, date and venue of the pictures,' said Professor Park Young Ho, of the state-run Korea Institute for National Unification.

Seoul's National Intelligence Service believes the North Korean leader has undergone brain surgery following a stroke in mid-August but is recovering well.

There are fears in both South Korea and Japan that he is losing his grip on power in the isolated communist country and that the region could face instability should he die abruptly without a clear successor.

North Korea has denied the speculation, and recently mounted a campaign to show he is healthy and in control.

The first batch of pictures was released last month, showing Mr Kim inspecting a military unit. They were undated, but the lush green foliage in the background raised questions as it appeared not to fit with the Korean peninsula's autumn season, which began in September.

The second batch of pictures was released on Sunday, showing what North Korean media said was Mr Kim visiting a sports stadium and watching a football match. The venue and date of the event were not revealed.

The latest batch of photographs released yesterday showed him posing with groups of troops. The North's official Korean Central News Agency (KCNA) did not say when he made the visits.

The photos released on Sunday and yesterday show trees with autumn foliage in the background.

'North Korea released all these photographs, including the ones on Wednesday, to show that Kim Jong Il is still in the driver's seat,'said Professor Lee Sang Hyun, director of the Security Studies Programme at Sejong Institute, a think-tank. 'The pictures of his visit to two separate army units send the message that he is healthy enough to be going from one place to another,' he added.

Experts on the North told The Straits Times that they often closely liaise with government officials to obtain information for their work, andexchange opinions with foreign experts. Diplomats are also good sources of information.

US chief nuclear negotiator Christopher Hill was in Pyongyang early last month to persuade the North Koreans to continue a denuclearisation process which they had appeared ready to ditch in September. When asked by reporters about Mr Kim's health, Mr Hill said: 'In August and September, we had difficulties getting answers from North Korea but answers were coming out again in October.'

That gave credence to the view that Mr Kim was temporarily unable to make a decision on the issue after being felled by a stroke in August, said observers.

The latest reports and pictures are unlikely to be the last.

'North Korea is shrouded in secrecy and there are still many things we do not know for sure,' said Professor Hyun In Taek of Korea University. 'We have to revise our views as new information surfaces.'

leeteejong@yahoo.com