North Korea's ailing leader Kim Jong-il has given his youngest son his first public title, naming him a general in a move analysts say marks the first stage of dynastic succession in the secretive state.

State media mentioned Kim Jong-un for the first time by name, but without identifying him as the son of the iron ruler, hours before the start of a rare ruling party meeting to elect its supreme leadership.

Kim Jong-il, 68, is believed to have suffered a stroke in 2008, but despite declining health shows no sign of relaxing his grip on power, underlined by his reappointment as secretary-general of the Workers' Party. Experts say his son is too young and inexperienced to fully take the reins.

"As expected, the dynastic transition is becoming public. So far, they are following the pattern we saw in the 1970s when Kim Jong-il himself was moving to become the new Dear Leader," said Andrei Lankov of Kookmin University. "The difference is that this time they seem to be in a great hurry."

Regional powers are watching the party conference, the biggest meeting of its kind for 30 years, for any sign of change in the destitute state's policies. Experts warn of potential infighting over the rise of the unproven young Kim.

State news agency KCNA said Kim had issued a directive bestowing military rank on six people, including promoting Jong-un and the leader's sister Kyong-hui to general in one of the world's largest armies.

The son is believed to have been born in 1983 or 1984 but little is known about him, even by intensely secretive North Korean standards, beyond the sketchy information that he went to school in Switzerland and is his father's favourite.

By signalling the young Kim's rise, experts say North Korea is readying for a collective father-and-son leadership.