Trading of iron ore derivatives on China's Dalian Commodity Exchange advanced to a record last month amid increased volatility.

Volumes surged 54 per cent in July from a month earlier to 32.4 million contracts, or 3.2 billion metric tons, according to bourse data. The previous record was in May, when 24.9 million contracts traded. Volumes more than tripled from a year earlier.

Iron ore has been whipsawed in recent weeks as investors weigh lower inventories at ports in China against signs that the economy is slowing. Prices tumbled to a six-year low in early July before rallying into a bull market at the end of the month. While trade on the Dalian bourse is restricted to citizens and companies registered on the mainland, the exchange plans to allow foreign access as it seeks to extend its influence over global raw-material prices.

"Iron ore futures volume reached a new high because investors are quite split in terms of price outlook," said Guo Junwen, analyst at Galaxy Futures in Shanghai. "Recent economic data has painted a bearish picture while port stockpiles are hovering near the lowest since November 2013. We will see the market fluctuate with high volumes as the two sides can't seem to agree with each other."

Most-active futures in Dalian fell 1.1 per cent to close at 363 yuan ($US58.46) a ton on Monday, extending a 12 per cent slump in July which was the first back-to-back monthly drop since November. Ore with 62 per cent content in Qingdao entered a bull market last week after rebounding from $US44.59 a dry ton on July 8, the lowest level since at least May 2009, according to Metal Bulletin Ltd. Spot prices were at $US53.41 a ton on Friday.

Iron ore's 10-day volatility jumped to a record 94.4 on July 13 and price fluctuations tracked over 30, 50 and 100 days surged to the highest ever, data compiled by Bloomberg show.

Inventories at Chinese ports shrank 0.6 per cent last week to 81.95 million tons, data from Shanghai Steelhome Information Technology show. Stockpiles sank to a 19-month low of 79.35 million tons in June and have decreased 19 per cent this year.

Dalian started trading iron ore futures in 2013, challenging cash-settled contracts offered by Singapore Exchange, CME Group and Intercontinental Exchange.