China has expressed anger over sanctions imposed by the United States on a Chinese firm for selling refined petroleum products to Iran.

China's foreign ministry criticized the unilateral sanctions imposed on Zhuhai Zhenrong based on US law, calling them 'unreasonable'.

"Imposing sanctions on a Chinese company based on a domestic (US) law is totally unreasonable and does not conform to the spirit or content of the UN Security Council resolutions about the Iran nuclear issue," The BBC quoted Foreign Ministry spokesman Liu Weimin, as saying.

"China expressed its strong dissatisfaction and adamant opposition," he added.

The US said on Thursday that Zhuhai Zhenrong was one of three international firms to be punished for dealing with Iran.

The US state department said the sanctions, preventing the firms from receiving US export licences, US Export Import Bank financing or any loans over 10 million dollars from US financial institutions, were part of efforts to persuade Iran to rein in its nuclear ambitions.