"Kim arrived at about five this morning," said an official at the Friendship Bridge tourist site at northeastern Chinas Dandong border crossing with North Korea.

"We received a notice from the Public Security Bureau and the army that we should shut down tourist operations in the morning (when Kims train came over from North Korea)," the official told AFP by telephone.

It is Kims first trip in more than four years to China, the Norths main source of finance, food and fuel and which is seen as one of the few nations able to put pressure on Pyongyangs hardline regime.

Rail officials in Chinas Liaoning province also confirmed that a special train from North Korea crossed into the country on Monday, but the Chinese foreign ministry refused to immediately say that Kim had arrived.

Analysts said China could press Kim to return to the six-party nuclear disarmament talks it hosts in return for badly needed aid for his impoverished communist nation.

Kim, who is said to dislike air travel, has visited China four times since 2000 by train. The last trip in January 2006 was shrouded in secrecy and only formally announced after it had ended.

North Korea has suffered from persistent food shortages since its former benefactor the Soviet Union collapsed almost 20 years ago. Ongoing shortages were further aggravated last November by a bungled currency reform.

Kims visit comes after Chinese President Hu Jintao on Friday met South Korean President Lee Myung-Bak and also held talks with North Koreas number two leader Kim Yong-Nam on the sidelines of the World Expo in Shanghai.

Tensions on the Korean peninsula have been rising since the mysterious sinking of a South Korean warship near the disputed sea border with North Korea on March 26, with suspicion falling on Pyongyang.

According to South Koreas Yonhap news agency, citing sources in Seoul and Beijing, a 17-carriage train crossed the Yalu border river into Dandong at 5:20 am (2120 GMT Sunday) amid tight security.

The train was thought likely to be headed to the booming eastern Chinese port city of Dalian en route to Beijing, Yonhap said.

"The special train from North Korea, we are not clear about when it will come ... the leaders dont tell us," an official at Dalian railway station told AFP on condition of anonymity.

"Normally I can tell you anything you want, except now, I cannot tell you the details of this special train from North Korea."

China was likely hoping to show Kim the booming economic growth in Dalian, a city that lies only about 300 kilometres (180 miles) due west across the Yellow Sea from the North Korean capital.

"Kim will likely express his commitment to returning to six-party talks while leaving a date for the return up to host China," said Yang Moo-Jin of Seouls University of North Korean Studies.

"In return, Kim will receive economic aid from China."

The North angrily quit the talks in April last year and vowed to restart production of weapons-grade plutonium, carrying out its second atomic weapons test the following month.

Pyongyang says it will not go back to the nuclear dialogue until UN sanctions are lifted, and until the United States makes a commitment to hold talks on a formal peace treaty.

North Korea had agreed in previous rounds of talks -- which group the two Koreas, China, Russia, the United States and Japan -- to end its nuclear weapons drive in return for security guarantees and badly needed fuel aid.

US and South Korean officials have indicated the talks cannot restart under a cloud of suspicion about the Norths involvement in the sinking of the warship Cheonan which cost the lives of 46 sailors.

The South has not so far directly accused the North over the sinking and Pyongyang has angrily denied responsibility.