Inventories of iron ore at 25 of China's major sea ports rose to 94.93 million tons in the week ending July 11, according to the Xinhua-China Iron Ore Price Index released on Tuesday.

The stock of imported iron ore last week was 810,000 tons higher than one week earlier, or up 0.86 percent week-on-week, according to the index compiled by the Xinhua News Agency to track iron ore inventories and imports on Chinese spot markets.

The prices of imported iron ores also increased last week, although sales of steel products are traditionally slack in July. The index for 63.5-percent-purity and 58-percent-purity iron ore imports both rose by 4 points to hit 179 points and 148 points, respectively.

The increase in prices was partly due to higher operation costs of mining giants in Australia as the country will impose a carbon dioxide tax on 500 big companies next year.

Reduced shipments from BHP Billiton also helped push up iron ore prices. The world's third-largest mining company by market capitalization halted operations at its Port Hedland docks after one worker was crushed by a crane at the export docks on July 7.

Prices of imported iron ores are likely to fluctuate in the short term, Xinhua analysts said.