SEOUL - NORTH Korea's state media stressed the 'inheritance of bloodline' in an editorial marking the 67th birthday of leader Kim Jong-Il, a South Korean official said on Tuesday.

Analysts said the language used in the ruling communist party newspaper Rodong Sinmun is unusual. It comes amid increasing speculation about the future leadership after Kim reportedly suffered a stroke last August.

Mr Kim inherited power from his father Kim Il-Sung in the communist world's only dynastic succession. But it is unclear whether he wants one of his three sons to succeed him - and if so, which one.

Yonhap news agency reported last month that Kim had nominated 25-year-old Jong-Un as his successor, in preference to the eldest Jong-Nam and the middle son Jong-Chul.

'This year's editorial frequently used such expressions as the inheritance of bloodline of Mount Paektu, future of the revolution or inheritance of the tradition,' said unification ministry spokesman Kim Ho-Nyoun.

Last year's editorial had merely called for unity around Mr Kim and heaped praise on his army-first policy.

'Such expressions used by North Korean newspaper editorials marking Kim's birthday are rare and unusual,' Kim Yong-Hyun, a North Korea studies professor at Dongkuk University, told AFP. 'But it is premature to say Monday's editorial is definitely referring to the succession, and we cannot interpret it as a clear indication that the succession is under way.'

Mount Paektu on the China border is held sacred in the hardline communist country as Kim's birthplace, even though analysts say he was born in Russia.

'Prospects for the revolution of juche are bright in the midst of the glorious inheritance of the bloodline of Paektu,' the editorial said.

Juche or self reliance is the country's guiding philosophy adopted by founding president Kim Il-Sung, who died in 1994.

'As the revolutionary tradition of Paektu is being inherited strongly, our revolution vigorously maintains its lifeline even though generations and centuries change and the condition and climate of our struggle are different,' it said.

Mr Kim is said to have recovered well from his stroke and still to be in control of his nuclear-armed but impoverished nation.

Choson Sinbo, a pro-Pyongyang newspaper published in Japan, reported Tuesday that he led a climbing party for several kilometres after inspecting a hillside park in Pyongyang on January 17.

Some analysts believe a collective military-party leadership will emerge if he dies or becomes incapacitated, with one of the sons as a figurehead leader. -- AFP