The premiers of China and Japan agreed Monday to set up a hotline following a series of tense naval incidents, and to resume formal talks on jointly exploring offshore gas and oil fields.

Japan and China, the world's second- and third-biggest economies, are rivals for resources and have competing claims to parts of the East China Sea.

Premier Wen Jiabao met his Japanese counterpart Yukio Hatoyama in Tokyo weeks after Chinese naval helicopters twice buzzed Japanese destroyers, and a Chinese marine survey ship pursued a Japanese coastguard vessel.

"Our prime minister said the recent Chinese activities near Japan had raised concerns," a Japanese foreign ministry official said following the talks.

Hatoyama had "requested that such actions never be repeated," said the official, who asked not to be named, adding that Wen had offered no reply.

"The two sides agreed to set up a hotline so that telephone conversations can be made without any delay. The Chinese side said they always want to exchange views on important subjects."

The new hotline would be between political leaders, not defence chiefs.

Japan has eyed China's military build-up -- with annual double-digit growth for most of the past two decades -- with concern and repeatedly called on the country to increase the transparency on its defence spending.

The helicopter incidents in April came as Japanese destroyers were watching a Chinese flotilla, including submarines, sailing in international waters between Japanese southern islands, an act seen as provocative by Tokyo.

Wen in a speech Monday pledged that "We will never become a threat to any countries. We will never aim for hegemony. This is our policy."

Hatoyama also again urged Wen to support efforts to reprimand North Korea, which has been blamed for the sinking of a South Korean warship in March, killing 46 sailors -- a call Beijing has so far resisted.

"Our prime minister said he believes in the results of the joint investigation in South Korea. He said North Korea should be strictly criticised under international rules," said the Japanese official.

"The Chinese side said they want to maintain communications between China and Japan on the issue."

Wen and Hatoyama also agreed Monday to resume stalled talks on a June 2008 agreement to jointly explore oil and gas resources in the East China Sea, in the Shirakaba oil and gas field, known as Chunxiao in Chinese.

There has been no joint progress and Japan says China has started unilateral operations on its side of the median line, with ships reportedly observed taking equipment to the area.

The leaders also signed agreements on food safety, energy conservation, environmental protection and e-commerce.

The food safety agreement comes after pesticide-tainted Chinese dumplings made 10 people ill in Japan in 2007-08. Chinese police in March arrested a Chinese suspect in the case.

Under the agreement, officials from each country will be allowed to conduct on-site inspections of food-processing plants in the other.

Despite their differences, China and Japan have been at pains to highlight their strengthening ties.

Hatoyama has urged turning the East China Sea into a "Sea of Fraternity," and Wen on Sunday read a haiku-style poem that likened changes in bilateral ties to a spring thaw after a winter freeze.

Wen started Monday early, practising tai chi and jogging in Tokyo's Yoyogi Park, where the premier, dressed in black sportswear and shadowed by bodyguards, shook hands with other early risers.

In a bout of "baseball diplomacy," he played catch with university students and practised batting.

China is expected to overtake Japan as the world's number two economy this year. Demand from China and other emerging Asian markets has driven Japan Inc's recovery from its worst post-war recession.

China is Japan's top trade partner, with two-way business around 230 billion dollars last year, exceeding Japan-US trade for the third year in a row.

Wen said in a speech that "a stronger Chinese economy will benefit Japan."