(CNN) -- North Korean leader Kim Jong Il was visiting China on Friday, a South Korean official said, according to state-run Yonhap news agency.
The report contradicts earlier ones that Kim's son and heir apparent, Kim Jong Un, was leading the visit. It was unclear whether his son was accompanying him.
According to Yonhap, the trip would be Kim Jong Il's third to China in a little over a year.
The news follows last week's revelation that South Korean President Lee Myung-bak has officially invited Kim Jong Il to attend a nuclear security summit in Seoul next year.
South Koreans pay close attention to the movements of the leadership of North Korea, perhaps the world's most secretive regime. North Korean state media is often slow in reporting the Kims' activities.
Open Radio for North Korea, a South Korean non-governmental organization, said Kim was visiting China. The organization is partly staffed by defectors from the North. It maintains a network of informants in North Korea.
"I checked through my sources, and one had heard from a military officer working at the border yesterday that there was some kind of 'emergency' along the border," said Ha Tae-kyung, the organization's president. "According to that military officer, it was Kim Jong Il who is going -- not his son."
His account and the South Korean news agency report could not be independently verified.
The term of Chinese President Hu Jintao's term is set to expire next year, prompting some to anticipate greater diplomatic interchange between Beijing and Pyongyang as Kim seeks to forge relations with the incoming leader.
It's clear that North Korea needs help, analysts said.
"Kim Jong Il wants to get something from South Korea or the U.S. or China -- economic aid or security assurances -- but at the moment he is not getting anything and China is preventing North Korea from further provocations," said Choi Jin-wook of Seoul's Korea Institute of National Unification. "Kim wants to know what China is going to do for them."
Heavily sanctioned following several nuclear and missile tests, Pyongyang has been reaching out to South Korea in recent months -- experts say the hardline state is desperate for a resumption of food aid.
However, its customary form of leverage -- provocations -- is being restrained by Beijing, And six-party talks, which would offer economic incentives in return for North Korean denuclearization, have been in limbo for more than two years.
Former U.S. President Jimmy Carter, who visited Pyongyang and Seoul last month, carried a message from Kim to South Korea's Lee, in which the North Korean leader said he was ready to meet with the South's president "without preconditions."
Seoul's policy is to refuse high-level contacts until North Korea apologizes for two incidents last year that killed 50 South Koreans. South Korea accuses the North of torpedoing and sinking one of its warships in March 2010, killing 46 sailors. In November, North Korea shelled Yeonpyeong Island, killing two South Korean marines and two civilians.
Last week, however, Lee invited Kim to visit South Korea.
"The South Korean government did deliver a message of our invitation to North Korea's leader to visit next year's Nuclear Security Summit in Seoul," the foreign press officer from the presidential office said.
Few, however, expect Kim -- a virtual recluse whose political decisions are made behind closed doors and who is reportedly paranoid about personal security -- to engage in such high-profile, transparent statesmanship as an international nuclear summit, or to visit Seoul.
The last two inter-Korean presidential summits took place in Pyongyang.