With Beijing questioning major miners on their role in record-high prices that are squeezing steel mill margins, Anglo-Australian iron ore miner Rio Tinto  says it expanded its iron ore shipments and on-demand sales to meet increased demand for the steelmaking ingredient in China this year.

On Tuesday, China Iron & Steel Association (CISA), the domestic steel industry association, held a video conference with Rio, one of China&rsquo s biggest iron ore suppliers, days after an online meeting with rival miner BHP  , and said the current ore price was &ldquo unreasonable&rdquo .

That price stood at about US$153 per tonne on Wednesday, after reaching nearly US$160 a tonne last week &ndash about double the price at the start of the year.