An intensifying crackdown on corruption in China is a positive development that should be welcomed by companies doing business there, and not be a source of concern, said a senior UN crime-fighting official.

Some foreign firms in China are getting increasingly jumpy about a spate of corruption and anti-trust investigations by Chinese authorities and are hiring lawyers to make sure their operations comply with the law.

Graft investigations have targeted the pharmaceutical industry while authorities have also launched a major probe into China's leading oil and gas company.

Dimitri Vlassis, head of the corruption and economic crime branch of the Vienna-based UN Office on Drugs and Crime (UNODC), said corporate leaders should use the campaign against graft as an opportunity for reform.

"The (Chinese) authorities are taking this issue very, very seriously and they have increased their anti-corruption drive more generally in visible ways in the past couple of years," he said in a telephone interview.

Companies should welcome this and review internal processes, he said, but make sure this was not simply an issue of complying with the law.

"It is also a matter of actually doing the right thing and engaging in competition based on a set of ethical principles, ethical behavior," Vlassis added, advocating corporate zero-tolerance of graft.

Chinese President Xi Jinping, who took office in March 2013, has made fighting corruption a central theme of his administration.

"What I see are very important and consistently determined steps forward," Vlassis said.