Microsoft described the new regulation as "extremely unexpected" on Tuesday afternoon.

"We have been working proactively with the Central Government Procurement Center and other government agencies through the evaluation process to make sure that our products and services meet all government requirements," the world's largest software company told China Daily in an e-mailed statement.

"We are also working closely with relevant departments to evaluate Windows 8 for government purchase in the future."

Wide use of overseas software in governments, military projects and crucial industries such as energy has been raising security concerns for the Chinese government since last year.

Industry regulators have been openly calling for made-in-China systems for many years. The latest public support came from the Ministry of Industry and Information Technology Spokesman Zhangfeng. He pledged in mid-May that the ministry will put "increasing focus" in helping Chinese companies develop Linux-based OS in a bid to lower safety risks.

"The issue of security of foreign software products is not an unnecessary self-inflicted one," said Liu Yufeng, executive deputy general manager of Guangzhou-based ZWCAD Software Co, which develops computer-aided design and manufacturing products.

"Software backdoor may pose risks to the government, national defense, the military industry and other businesses," Liu said.

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