China still has room to raise the level of cash that banks must put to one side rather than lend out as a way of cooling the economy, central bank governor Zhou Xiaochuan said in remarks published on Thursday.

The authorities could take further steps to tighten liquidity conditions at a time of their choosing, the Shanghai-based Oriental Morning Post cited Zhou as saying.

"Currently, there is still room to raise banks' reserve requirement ratios and we can use such a monetary tool at any time," he told the newspaper.

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"But it doesn't necessarily mean we have to use these tools right now."

Beijing has already raised the amount of funds that lenders must park with the central bank seven times since June 2006 as part of a campaign to prevent credit and investment growth from destabilising the world's fourth-largest economy.

Many analysts expect the authorities to tighten monetary policy further in the weeks ahead, either by raising banks' reserve requirements or benchmark interest rates. An acceleration in fixed-asset investment growth to 25.5 percent in the first four months filled the country's strong growth picture, according to official data issued on Thursday.

Data released recent days has showed that lending and credit growth remains elevated and that China's trade surplus widened to $16.9 billion in April from a surprisingly low $6.9 billion in March.

China's domestic A-share market, which has more than tripled in value since early 2006, has fuelled speculation that the government may raise interest rates sooner rather than later.

Asked about his views of the stock market, Zhou said that it was none of his business.