North Korea's Kim Jong-Il stopped in China's Nanjing city Tuesday after touring an industrial zone and browsing at a store, reports said, on a trip believed aimed at studying the country's economic boom.

Kim's multi-city tour is his third China visit in just over a year and the repeat appearances are widely viewed as a bid by impoverished North Korea for more trade and economic help from Beijing, its sole major ally and benefactor.

As Kim reached Nanjing, a US government team arrived in North Korea to assess its requests for food aid after UN agencies and charities reported that millions in the economically dysfunctional nation need urgent assistance.

"Where can I find salad oil?" Kim, wearing his trademark dark sunglasses, asked sales clerks in a shopping mall in the eastern city of Yangzhou on Monday, according to a report by Japan's Kyodo news service.

Kim, 69, "looked around at daily necessities, including rice and cooking oil", South Korea's Yonhap news agency said, adding that he bought nothing.

Kim, who arrived in China by train on Friday, travelled from Yangzhou to nearby Nanjing, capital of Jiangsu province, on Tuesday in a roughly 40-car convoy with an armed police escort, Yonhap said.

He later visited a Nanjing manufacturer of mobile phones, television sets and other electronics, it added.

A North Korean special train believed to be carrying Kim departed Yangzhou later Tuesday heading in the direction of Beijing, Kyodo reported.

While in Yangzhou, Kim had dined with former Chinese president Jiang Zemin, who was born in the city, and visited manufacturers, Yonhap said.

Details of Kim's China visits are shrouded in secrecy with details divulged by both sides only after his return home.

A Chinese foreign ministry spokeswoman on Tuesday also declined comment on Kim's itinerary or other details, but told a regular press briefing in Beijing that healthy bilateral ties was China's "unswerving policy".

North Korea's state-planned economy is crippled by severe shortages of power, raw materials, and persistent food shortages.

During Kim's previous visit in August, Chinese President Hu Jintao urged him to undertake economic reforms. Chinese Premier Wen Jiabao said Sunday in Tokyo that Kim was invited to help Pyongyang learn about China's economic development and revive its own economy.

Overseas aid for North Korea is waning due to anger at its nuclear and missile development. Sanctions have been imposed to curb those programmes.

Six-nation talks aimed at dismantling the nuclear programme in exchange for diplomatic and economic benefits have been stalled for more than two years.

The US delegation that arrived in North Korea on Tuesday is headed by Robert King, special envoy on the North's human rights, and Jon Brause, an official with the US Agency for International Development.

The delegation would "consult on humanitarian issues", the North's official news agency said in a one-sentence report. The US State Department last week said King would also raise human rights issues.

Kim Yong-Hyun, a professor at Seoul's Dongguk University, cautioned against expecting any imminent changes in Pyongyang's economic policies.

"Through this visit, Beijing is urging North Korea to accept China-style economic openness and reform but the North, in reality, cannot shift to a market-oriented economy in the foreseeable future," the professor said.

While the North may allow limited reform in specific areas like the Rajin-Sonbong special economic zone near the Chinese border, it will not ease its Stalinist controls over the nation's 24 million people, he added.

Yonhap said North Korea and China would break ground later this week on a joint project to turn Hwanggumpyong, an island in the Yalu River on their border, into an industrial complex, and quoted sources saying Kim may attend.

The North Korean leader also is believed to be keen to shore up Beijing's support for a plan to eventually transfer power to his son and designated successor, Kim Jong-Un.

Various reports have indicated the heir apparent was not travelling with his father in China.

burs/mtp