U.S. Secretary of State Hillary Clinton on Thursday raised the possibility of a power struggle in North Korea, saying "the whole leadership situation is somewhat unclear".

North Korean leader Kim Jong-il, 67, is widely believed to have suffered a stroke in August, although he appears to have recovered. Kim has given no indication who will take over in Asia's only Communist dynasty.

Following are profiles of some possible successors. Intelligence officials say the three men most likely to replace him are his youngest and eldest sons and a brother-in-law.

THE YOUNGEST SON

Kim Jong-un was born in late 1983 or early 1984. The Swiss educated Jong-un is believed to be the favourite of his father, who reportedly considers him intelligent and thoughtful. Last month the South's Yonhap news agency said leader Kim had picked Jong-un to succeed him, although his youth has been cited as a problem in a society where the tradition of seniority is strong.

There has been no confirmation of the Yonhap report and intelligence officials cautioned that no candidate had emerged as the favourite. However, South Korean and Japanese media recently reported Jong-un might be nominated for a seat on the Supreme People's Assembly, the North's rubber stamp parliament, which will elect new delegates on March 8.

That would introduce him to the North Korean public and place him in a prominent role in the leadership class.

THE ELDEST SON

Many believe Kim Jong-nam, 37, fell out of favour when he was deported from Japan in 2001 on suspicion of trying to enter the country using a forged Dominican Republic passport in a bid to see Tokyo Disneyland.

The easy-going and portly Jong-nam has spoken to reporters several times over the last year, answering questions in Korean and near-perfect English. His father has often asked Jong-nam, who spends about half of his time outside of North Korea, to run tasks overseas, an intelligence source said.

BROTHER-IN-LAW

Jang Song-taek, 63, husband of Kim's sister and a senior communist party official, is largely expected to play a major role in the leadership that survives Kim Jong-il, possibly as a caretaker or as the outright leader. He is often seen as one of the most powerful men in the ruling party structure, although he officially holds a nominal and relatively minor post.

Jang has been mentioned often in North Korea's official media as joining Kim on his field visits over the past months while one of his allies was named the North's new defence minister.

HEAD OF STATE

Kim Yong-nam, 81, is head of the North Korean parliament's leadership council and is the country's nominal head of state. While a long-time party member and a former foreign minister, he is not thought to have the legitimacy rooted in the North's revolutionary history, seen as necessary to become leader. If he did succeed Kim, it would likely be as a figurehead.

COLLECTIVE LEADERSHIP

Experts say North Korea could move into a collective leadership when Kim Jong-il dies with one of his sons named as figurehead leader but real power held by a group of officials from the ruling Workers' Party and the military.

Kim's inner circle is dominated by cadres in their 70s and 80s who could oversee a caretaker government.

MILITARY RULE

The military could take over. During his 15-year rule, Kim has used the "Songun" or military-first doctrine to cement his grip on office, which he holds as chairman of the National Defence Commission and the 1.2 million-strong Korean People's Army, as well as head of the communist Korea Workers' Party. His dead father Kim Il-sung is officially the country's eternal president. The doctrine has given his military a strong grip on power. But the military is also seen as segmented along generational lines and divided by factions loyal to one or another of Kim's sons.