JOIN USChina is regarded as Pyongyang's close ally. North Korea ties with South Korea has also strained over the sinking of naval ship close to the Communist nation's coast.
Kim, who had aversion to air travel arrived in China by his personal train and expected to visit Shanghai expo and his arrival was confirmed by the Chinese railway officials at the Friendship bridge near the border between the two countries.
Tourist operations between the two countries were stopped during his arrival. This is his first trip in four years to China.
Beijing continued to maintain close relations with the estranged Communist country providing generous financial, food and fuel assistance.
His visit to China were always shrouded in secrecy and often confirmed only after his return to Pyongyang.
Considering Beijing's close ties, US and its allies often looked for China's support in the six party negotiations aimed roll back Pyongyang's nuclear programme threatening Japan and South Korea.
North Korea is currently refusing to return to six-party talks. Tensions are also running high with South Korea, after sinking of one of its warships last month in which 46 sailors were killed.
South Korea has said that the talks could not restart if evidence emerges that North Korea was responsible for sinking the warship.
Significantly Kim's visit is taking place two days after Chinese President Hu Jintao met South Korean President Lee Myung-Bak in Shanghai where Bak came to attend the Expo inauguration.
Hu also met North Korea's number two leader Kim Yong-Nam on the sidelines of the World Expo. Speculation is rife that Kim may visit the Expo.
Observers here say that that Kim is also expected to seek economic assistance from Beijing to deal with soaring inflation in his country aggravated by bungled currency reforms last year.