SINGAPORE - Singapore and China signed on Wednesday several pacts to increase cooperation in areas ranging from taxation to water management.

Under the pacts, the two countries -- which are also in talks for a free-trade agreement -- will amend laws to avoid double-taxing investors' income.

Other areas covered were health quarantine, water management research and training of Chinese officials in urban planning, environmental protection, finance and taxation.

"Singapore is an important cooperation partner of China. Deepening cooperation...is conducive to the stability, development and prosperity of the region," China's Vice Premier Wu Yi, who witnessed the signing, told reporters and delegates.

Wu is on a four-day visit to Singapore ending on Thursday, and is accompanied by Commerce Minister Bo Xilai and Vice Minister of Finance Zhang Shaochun.

Wu said Singapore had invested $31 billion in China by the end of May this year, which makes the Southeast Asian city-state China's sixth-largest source of foreign direct investment.

Singapore has also trained more than 9,000 Chinese officials, Wu said.

She met Prime Minister Lee Hsien Loong, who has said he is eager to conclude the trade pact talks that started last year.

Lee said a free-trade pact would boost ties and strengthen China's relations with the 10-nation Association of South East Asian Nations, or ASEAN.

Wu met Lee Kuan Yew on Wednesday. Lee is modern Singapore's first prime minister, and chairman of the Government of Singapore Investment Corp. (GIC), which manages more than $100 billion of the country's foreign reserves.

China plans to set up a state investment agency that could be similar to Singapore's state investor Temasek or the GIC., to invest part of its $1.2 trillion of foreign exchange reserves -- the world's largest.

The Chinese government has said Temasek would be one of the models for the new vehicle and Chinese officials have previously visited Singapore to take a look at how it invests state funds.

China was Singapore's fourth-largest trading partner in 2006, with total trade amounting to S$85 billion ($56 billion), trade agency International Enterprise Singapore said.