Bing was the only major foreign search engine accessible from within China's so-called Great Firewall, with Microsoft censoring search results on sensitive topics, in accordance with Chinese government policy.
Google is now in the midst of developing a search engine that complies with China's censorship laws, although the move has faced strong opposition from employees and human rights activists alike.
Smith said Microsoft isn't certain whether the blocking of its search engine "is confined to Bing or if it is something that is broader".
But the analyst said it could also be a "hack gone wrong".
Bing's rival Google shut down its search engine in China in 2010, after rows with the authorities over censorship and hacking.
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Chinese filters block access to global social media including Twitter, Facebook and YouTube.
Xi's government also has tightened controls on use of virtual private network technology that can evade its filters. On the other hand, Google is now believed to be exploring a return to China with a dedicated service tailored to China, though at this point, plans are said to be in their early stages. "Thank you wise party leaders!" Microsoft didn't immediately respond to a request for comment but is reportedly investigating the matter.
Credit: Casimiro PT/ShutterstockMicrosoft's Bing search engine has been unexpectedly blocked in China without any official statement from the government.
"The fact that Bing is run by Microsoft, which is not a Chinese company, means that Beijing has less leverage over the company, compared to say Baidu", said Lokman Tsui, an assistant professor at the Chinese University of Hong Kong.
"Periodically there are issues that arise and sometimes those issues do lead to our service or some other services being blocked and you know it is an area where we understand we don't have the same legal freedom that we do in other countries but at the same time we stick to our guns", he said.
"Given Washington's bid to contain Huawei, China is sharpening its moves against the American tech industry, especially those affiliated with Silicon Valley", Tom Fowdy, an independent Beijing-based political analyst, told AFP.