Kim Jong-il, the "Dear Leader" of the world's most secretive country, was absent, an unprecedented failure to appear at such a high profile event in a country ruled through a mix of personality cult and rabid nationalism.

The no-show has given speculation over recent weeks that Mr Kim, 66, is gravely ill, proper credibility.

North Korea's state media was silent about his absence from the parade, a relatively low-key ceremony that unexpectedly lacked much of nuclear-armed North Korea's trademark thundering military prowess.

In a broadcast monitored in Seoul, Korean Central Television showed North Korea's deputy leader and other officials and military officers atop a viewing stand. Kim Jong-il was not shown.

In Washington, an intelligence official said it was possible that Kim was seriously ill. "There is reason to believe Kim Jong-il has suffered a serious health setback, possibly a stroke."

It was reported earlier this week that five Chinese doctors dispatched from Beijing to Pyongyang, the North Korean capital, had yet to return home.

North Korea's state news agency made no mention of Mr Kim appearing in public yesterday. Mr Kim's last appearance reported by North Korean media came on 14 August.

South Korean news media, citing government officials, have said that he may be receiving medical treatment.

It is not the first time Mr Kim's public appearances have gone unreported for weeks at a time.

Mr Kim's health has been the focus of intense interest because his fate is believed to be closely tied to that of the secretive totalitarian state that he inherited in 1994 from his father in communism's first hereditary transfer of power.

Kim Jong-il took over the country after his father, Kim Il- Sung, died of heart failure – his death was not announced for 34 hours. The younger Kim has three sons by two mothers, but has not anointed any of them as his successor.

A spokesman for South Korea's National Intelligence Service said it could not immediately confirm Mr Kim's absence. The rally yesterday involved about one million people, the spokesman said. The centrepiece of the celebration had been expected to be a massive military parade through Pyongyang's central Kim Il-Sung Square, as normally happens in key anniversary years.

The footage broadcast on North Korean television showed what it described as uniformed civilian militia goose-stepping through the square, adorned with a huge portrait of Kim Il-Sung. Some military vehicles, which appeared to carry multiple rocket launchers, could be seen, though there appeared to be no heavy weaponry, such as tanks or missiles.

South Korea's Yonhap news agency reported on Monday that the military parade was expected to be the country's largest ever. Though it appeared to have been less than that, martial language was employed.

A man identified by Yonhap as Kim Yong Chun, North Korea's army chief of staff, said in a speech that the country would "continue to bolster its war deterrent" if the US and its allies did not give up what he described as their hostile policies against North Korea.

Mr Kim also said if a war broke out on the Korean peninsula again, the North's army would "mercilessly" defeat enemy forces, using rhetoric commonly employed by North Korean officials.

South Korea's intelligence service has previously said Mr Kim had chronic heart disease and diabetes – denied by Mr Kim himself. South Korea's Chosun Ilbo newspaper reported on Tuesday that Mr Kim collapsed on 22 August, citing an unnamed South Korean diplomat in Beijing. The diplomat got the information from a Chinese source, the paper said.

A Japanese scholar and expert on North Korea, Toshimitsu Shigemura, a professor at Tokyo's Waseda University, has even claimed recently that Mr Kim actually died in 2003 and that the North has been using body doubles of Mr Kim for public events since.

Jiang Yu, a spokeswoman for the Chinese foreign ministry said at a regular briefing yesterday that she had no information about Mr Kim's health, and had not heard that he was ill. She did not answer a question asking when Chinese officials last spoke directly with Mr Kim.

The North's 60th anniversary comes amid international doubts over its commitment to abandoning its nuclear programme and a worsening food crisis.

South Korea said last week the North had begun restoring its atomic facilities in apparent anger over not being removed from a US list of countries that sponsored terrorism.

North Korea – which conducted an underground nuclear test blast in October 2006 – began disabling its main nuclear facilities late last year in exchange for international energy aid and other benefits.

Family ties determine nation's future

IN THE event of Kim Jong-il's death, the future leadership and government of the impoverished state remain utterly opaque to those outside the regime.

What can be established is that there is no clear mechanism for the transfer of power outside Mr Kim's immediate family, but equally that the North Korean leader has not overtly groomed any of his children for such a role.

Kim Jong-chul, 27, is considered one possible such heir, the son of Kim Jong-il by his female companion, Ko Young-hee. The Swiss-educated Eric Clapton fan was made deputy chief of a leadership division of the Workers' Party in 2007.

Another possibility is Kim Jong-woon, younger brother of Jong-chul, born in 1983.

The Korean leader's eldest son, Kim Jong-nam, is believed to have recently come back into favour.

Born in 1971 to Kim's mistress, Song Hye-rim, Jong-nam was spurned by his father after being caught at Tokyo airport in 2001, travelling on a forged Dominican Republic passport and intending to visit Disneyland.

Attempted coups and army revolts are not unknown in North Korea, but the fact is the country's highly nepotistic regime is largely made up of members of the same families who threw off the yoke of Japanese imperialism and it is they, and their vested interests, who would decide the country's fate.

Reclusive tyrant has frustrated the West

KIM Jong-il inherited control of North Korea in 1994 upon the death of his father, Kim Il-sung, the founder of the reclusive communist state.

Cocooned in a personality cult at home, Mr Kim has long-frustrated the major powers during protracted talks about disabling North Korea's nuclear programme.

According to North Korean state media, Mr Kim boasts a photographic memory, has piloted jet fighters, composed operas and hit 11 holes-in-one in the first round of golf he ever played.

Officially, Mr Kim was born at a secret anti-Japanese guerrilla camp near Paektu-san, a now-revered mountain on the border with China, when the country was under Japanese control.

More likely, analysts say, he was born in the Soviet Union where his father and other Korean exiles were being trained.

By most accounts, Mr Kim has built up unchallenged power while the country suffered poverty, mass starvation in the 1990s and heavy reliance on foreign aid despite the national doctrine of "juche" that preaches self-reliance.

Mr Kim travels widely in North Korea, official reports say, but rarely goes abroad and then only by private train.

He is known to be a cinema buff, having directed several films and even kidnapped a director/actress from South Korea to help.

Mr Kim's bouffant hair, built-up shoes, chunky glasses and ill-fitting jumpsuits have made him the butt of jokes outside North Korea.

Foreigners who have met Mr Kim say he is clever, entertaining and very aware of events in the outside world.

George Bush, , the US president, has rarely concealed his dislike. At a meeting with Republican senators in 2003, Mr Bush called Mr Kim a "pygmy" and compared him to a "spoiled child at a dinner table". He has also called him a tyrant.