Rio Tinto could have been stealing China's steel industry secrets for as many as six years, according to a report on a website run by a State secrets watchdog.

It also accuses the multinational mining firm of costing the country 700 billion yuan ($102 billion) in excessive charges for iron ore.

The report was published on Baomi.org, a website affiliated with the National Administration for the Protection of State Secrets, on Saturday and written by Jiang Ruqin, ex-director of the Huai'an State secrets bureau in Jiangsu province.