SEOUL — North Korea's ruling communist party will pledge loyalty Thursday to the youngest son of leader Kim Jong-Il, a report said, ahead of the birthday of the man widely tipped to succeed his father.

The show of support for Kim Jong-Un, who turns 26 on Friday, will take place in the capital Pyongyang, said Opennews for North Korea, a Seoul-based media organisation run by North Korea watchers.

Party members have held a series of rallies in other cities this week to pledge loyalty to Jong-Un, NK Intellectuals Solidarity, a group of defectors, said in a report.

The South's unification ministry, which deals with cross-border relations, said it could not confirm the reports.

Meanwhile the North's Korean Central News Agency reported Thursday that mass rallies were held in various provinces this week, with speakers calling for solidarity "around the headquarters of the revolution" headed by Kim Jong-Il.

Party officials and others "vowed to thoroughly implement the militant tasks set forth" in a policy-setting New Year editorial by state newspapers, it said.

The regime has used Kim Jong-Il's birthday, a major national holiday, to stress loyalty to him.

Succession speculation has intensified since Kim senior, 67, suffered a stroke in August 2008. Widespread reports say he has chosen Jong-Un to inherit power.

There have been unconfirmed reports that Jong-Un has already been given a post in the communist party in preparation for his eventual takeover.

But some analysts say Pyongyang is waiting for the right opportunity to announce Jung-Un's nomination as eventual successor.

Kim Jong-Il, who took over after his father died in 1994 in a long-planned move, has three sons from two marriages, according to outside analysts.

Information is scant about Jong-Un, the second son of Kim Jong-Il's third wife Ko Yong-Hee. No adult photo of him is publicly available.

Some reports say Jong-Un, born in 1984, attended an international school in the Swiss city of Berne under a pseudonym.

Kenji Fujimoto, a former personal chef to Kim Jong-Il, has described the son as "a chip off the old block" who closely resembles his father physically and in terms of personality.

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