Heraldo de Madrid - North Korea's Kim makes unannounced visit to Chinese border city

Kim crossed via a major border bridge that only officially opened last week, 12 years after its completion, deepening economic ties between China and diplomatically isolated, nuclear-armed North Korea.

China is North Korea's largest trading partner and a vital source of diplomatic, economic and political support for Pyongyang, although ties have not always been smooth.

"It appears that Kim Jong Un has arrived in Dandong, China, via the New Yalu River Bridge," the unidentified government source said, without giving further details.

South Korea's Yonhap news agency also reported, citing an unidentified government source, that Kim had arrived in the northeastern Chinese city "earlier in the day".

AFP has contacted China's foreign ministry for confirmation.

The Korea JoongAng Daily newspaper, citing an unnamed South Korean government source, said Kim was greeted by Chinese Premier Li Qiang upon his arrival.

Kim is likely to return to North Korea the same day, Yonhap said, citing unnamed sources. South Korea's government told AFP it could not confirm his itinerary.

The four-lane bridge was completed in 2014 but its opening was delayed due to a lack of connecting roads and customs facilities on the North Korean side, according to South Korean news reports.

The opening of the new bridge came a little more than a month after North Korea and Russia opened their first road bridge, with Pyongyang lauding it as a sign of even closer ties after it sent troops to assist Moscow's full-scale war in Ukraine.

Kim's Dandong visit comes as world leaders prepare for November's APEC summit in China's Shenzhen, fuelling speculation over a possible meeting between the North Korean leader and US President Donald Trump.

It also takes place before Chinese President Xi Jinping and other top Communist Party officials meet in Beijing on Monday for an important gathering, the fifth plenary session of the powerful Central Committee.

- North-South tensions -

By meeting Li in Dandong, Kim "may have sought to reaffirm the economic cooperation agreed during Xi Jinping's visit to North Korea" earlier this year, and "press China to move more quickly on those commitments," Yang Moo-jin, former president of the South's University of North Korean Studies, told AFP.

"He may also have sought Beijing's active support and cooperation ahead of a possible summit with Trump in Shenzhen."

Hours before Yonhap's report on Kim's arrival in China, North Korea's state media said he had urged his military at a two-day meeting of company commanders in Pyongyang to train to become the strongest in the world.

Kim's call for what he dubbed a "Korean-style military revolution" came the same week Seoul's military proposed talks to clarify the border after an explosion inside the heavily fortified Demilitarised Zone (DMZ) further strained inter-Korean ties.

Seoul's military proposed the talks on Friday after it blamed the blast, which injured South Korean soldiers, on North Korean landmines. Pyongyang strongly rejects the claim.

North Korea has not responded to the proposal and previously rejected the South's demand for an apology over the explosion.

The countries remain technically at war as their 1950-53 conflict ended in an armistice, not a peace treaty.

- 'Implicit acceptance' -

Despite long-running UN sanctions, North Korea has enshrined its status as a nuclear-armed state in law, with its regime repeatedly declaring its atomic arsenal permanent and irreversible.

South Korea's dovish President Lee Jae Myung -- who has repeatedly offered Pyongyang talks without preconditions -- suggested in September that Washington seek a freeze, rather than the immediate elimination, of its nuclear programme in return for sanctions relief.

Critics say such an approach risks tacitly accepting North Korea as a nuclear-armed state while allowing Pyongyang to win sanctions relief without giving up its arsenal.

Analysts say China has also appeared to move towards implicit acceptance.

Kim hosted Xi in Pyongyang in June, soon after Xi held back-to-back summits in Beijing with Trump and Putin.

Neither Pyongyang nor Beijing mentioned North Korean denuclearisation in their official statements -- an omission experts saw as a sign of China's tacit consent.

I.Soto--HdM