China said Thursday that overseas companies were treated fairly under its anti-trust law, dismissing complaints that the country is skewing its business playing field against foreigners.

"All firms -- state-owned, private, foreign or multinationals -- are treated equally by the Anti-Monopoly Law and no one would get any preference," Shang Ming, head of the commerce ministry's anti-monopoly bureau, told reporters.

The ministry -- one of the three government agencies tasked to enforce the two-year-old law -- is in charge of reviewing and approving merger and acquisition cases.

The legislation requires firms to get Chinese government approval before a merger if their aggregate global revenue exceeds 10 billion yuan (1.5 billion dollars) or if their revenue in China exceeds two billion yuan.

Authorities also review the deal if two or more of the firms have each reported more than 400 million yuan of revenue in China in the previous fiscal year.

Shang said that so far, of the 140 or so cases reviewed since the law took effect in August 2008, only six had raised eyebrows -- all of them involving foreign companies.

In 2009, the ministry blocked US soft-drink giant Coca-Cola's 2.4-billion-dollar acquisition of Chinese beverage company Huiyuan Juice Group -- the only deal that has been rejected outright.

Five other deals received conditional approval and all the remaining applications were approved without restriction, Shang said.

The official said multinationals were not being targeted, but had received more scrutiny because they were industry heavyweights and their merger plans more often met the threshold requirement for government approval.

Shang's comments came amid rising concerns among foreign companies about the business environment in China, which some say is worsening for several reasons including what they say is discretionary enforcement of laws and regulations.

China's commerce ministry said in April that it had started an anti-monopoly review on a proposed iron ore joint venture between Anglo-Australian mining giants BHP Billiton and Rio Tinto.

Shang declined to comment on progress in that review on Thursday.

China is the world's largest importer of iron ore, and tensions over pricing between Chinese steel mills and major producers BHP, Rio and Brazil's Vale remain high.