Chinese regulators conducted new raids on Microsoft and partner in China Accenture, the agency said on its website on Wednesday, after confirming last week Microsoft is under investigation for anti-trust violations.
The State Administration for Industry and Commerce (SAIC) raided offices in Beijing, Liaoning, Fujian and Hubei, it said. The SAIC also raided the Dalian offices of IT consultancy Accenture, to whom Microsoft outsources financial work, according to the regulator.
"We're serious about complying with China's laws and committed to addressing SAIC's questions and concerns," a Beijing-based Microsoft spokeswoman said in an e-mailed statement.
Accenture also said it is involved in investigations.
"We can confirm that, as required by Chinese laws, we are cooperating with investigators of the State Administration for Industry and Commerce and are helping provide them with certain information related to one of our clients," Accenture Greater China said in an e-mailed statement, declining to elaborate.
Last week, the SAIC said it was formally investigating Microsoft for breach of anti-trust rules and had raided four of the software firm's offices in China.
Microsoft has been suspected of violating China's anti-monopoly law since June last year in relation to problems with compatibility, bundling and document authentication for its Windows operating system and Microsoft Office software, the SAIC said last week.
The SAIC declined to provide further comment when contacted by phone on Wednesday.
Microsoft Deputy General Counsel Mary Snapp was in Beijing to meet with the SAIC on Monday, where the regulator warned Microsoft to not obstruct the probe.
But industry experts have questioned how exactly Microsoft is violating anti-trust regulations in China, where the size of its business is negligible.
The US company has taken a public beating in China in recent months. It has been subject to wider scrutiny of US technology firms in China in the wake of former US National Security Agency contractor Edward Snowden's cyber espionage revelations.
It has also seen its OneDrive cloud storage service disrupted in China, and had its latest Windows 8 operating system banned from being installed on the central government's new computers.
The Microsoft investigation comes amidst a spate of anti-trust probes against foreign firms in China, including mobile chipset maker Qualcomm and German car maker Daimler AG's luxury auto unit Mercedes-Benz.
China is intensifying efforts to bring companies into line with an anti-monopoly law enacted in 2008, having in recent years taken aim at industries as varied as milk powder and jewellery.
China on Wednesday said it will punish foreign car makers Audi, owned by Volkswagen and Chrysler as well as some 10 Japanese spare-part makers for anti-trust violations.
A number of multinational companies including Mead Johnson Nutrition and Danone have been slapped with substantial fines following similar investigations in the past.