BEIJING -- Dalian Commodity Exchange (DCE) will closely monitor the commodity market to stop illicit trading, said vice general manager Wang Fenghai Thursday.

Wang said that spot prices of some commodities swung violently this year and he had seen signs of excessive speculation in the trading of coal and metal-related futures since April.

The DCE, one of China's four futures exchanges, has raised deposits and commission for heavily traded futures, among other measures to curb speculation and maintain market order.