China's competition regulator has given Microsoft 20 days to respond to its questions over "compatibility issues" with Windows and Office.

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Following claims by China's competition regulator last week that Microsoft wasn't fully cooperating with its probe into the software giant, it's now given Microsoft three weeks to start talking.

As noted in a report by Reuters, the State Administration for Industry and Commerce (SAIC) has spoken with Microsoft China vice president David Chen and subsequently demanded a "written explanation within 20 days" from Microsoft regarding questions over compatibility issues in Windows and Office.

SAIC officials have previously called Microsoft's Internet Explorer and its media player "problematic", in what appears to be a reference to software bundling — an issue Microsoft resolved in the US and Europe some years ago .

Microsoft reiterated to Reuters that it is "serious about complying with China's laws and committed to addressing SAIC's questions and concerns".

The investigation into Microsoft's operations in China follows raids on the company's Chinese offices in July and warnings from SAIC to Microsoft not to interfere with its investigation. SAIC has also visited Accenture's offices in China in search of Microsoft documents.

At the time, it was thought the investigation stemmed from Microsoft dropping support for Windows XP — an OS still widely used in China.

SAIC has since accused Microsoft of violating China's anti-monopoly laws since June 2013 over undisclosed compatibility issues in Windows and Office, in addition to bundling of software, and document authentication.

The anti-monopoly probe began shortly after the Central Government Procurement Centre banned government agencies from installing Windows 8 on PCs , apparently over security concerns.

While Microsoft CEO Satya Nadella plans to visit China later this month , it's not clear whether he will meet with Chinese regulators.

Microsoft's new obstacles in China come as the government reportedly begins ramping up efforts to build the nation's own operating system .

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