China's stocks slumped, driving the benchmark index down the most in six weeks, on concern the nation's property curbs and Europe's debt crisis will slow growth in the world's third-largest economy.

The Shanghai Composite Index retreated 108.23, or 4.3 percent, to close at 2,427.05, the most since May 17 and the lowest close in 14 months, after the Conference Board revised down its April gauge for China's economic outlook to indicate a weaker expansion. Declines deepened after the gauge fell below a technical support level at 2,481.

Jiangxi Copper Co paced losses by commodity producers after the New York-based research group said the leading economic index it compiles rose the least since November. China Cosco Holdings Co, the world's largest operator of dry-bulk ships, slid to the lowest since January as Citigroup Inc said Chinese exports face "strong headwinds." [China stocks 'range-bound' on exports, Citigroup says]

"Pessimism is growing about slowing economic and profit growth," said Dai Ming, a fund manager at Shanghai Kingsun Investment Management & Consulting Co.

The Shanghai Composite has tumbled 22 percent this quarter, heading for the biggest loss since the three months to March 2008, as policy makers tightened rules for the property market and concern grew that Europe's austerity measures will hurt demand in China's largest export destination. The equity index is the world's third-worst performer this year, down 26 percent.

Conference Board

The leading economic indicator for China rose 0.3 percent in April, less than the 1.7 percent gain reported on June 15, the Conference Board said. The previous release contained a "calculation error" for total floor space on which construction began, the research group said in a statement today.

"This correction doesn't affect our outlook for the Chinese economy," William Adams, resident economist for the Conference Board in Beijing, said in a telephone interview. "Growth was not likely to accelerate in China, and in fact, a moderation is possible. This correction also supports the same view."

Analysts are split on whether the People's Bank of China will raise interest rates this year from crisis levels after having increased bank reserve requirements, set a lower target for lending and eased the currency's peg to the dollar, according to a Bloomberg News survey last week.

Commodities, transport

Concerns over the prospect for growth sent copper and nickel both down by 2.2 percent. Crude oil prices also declined 0.6 percent to $77.79 a barrel.

China Cosco lost 2.5 percent to 9.03 yuan, pacing declines by transport companies. China Shipping Development Co, a unit of China's second-biggest sea-cargo group, slid 2.6 percent to 8.61 yuan. Air China Ltd, the nation's largest international carrier, retreated 5.4 percent to 10.51 yuan.

Chinese stocks will probably stay "range-bound" pending clarity on policies and the economy, Shen Minggao, head of China research at Citigroup, said in a report.

'Renewed turbulence'

The Shanghai Composite trades at 18.3 times reported earnings, compared with a multiple of around 33 times at the start of the year.

Global financial markets will face "renewed turbulence" as structural deficits and public debt in Europe and the US hamper economic growth, Aberdeen Asset Management said in a statement.