Microsoft Corp"s (MSFT.O) Bing search engine showed no image results for the query "tank man" in the United States and elsewhere on Friday, users reported, raising concerns about possible censorship around the Tiananmen Square crackdown anniversary. "Tank man" is often used to name an unidentified person famously pictured standing before tanks in China"s Tiananmen Square during pro-democracy demonstrations in June 1989. Microsoft said the issue was "due to an accidental human error and we are actively working to resolve this." Queries in Germany, Singapore and other countries also provided no results. China is known to require search engines operating in its jurisdiction to censor results, but those restrictions are rarely applied elsewhere. Rival Google showed several applicable results for "tank man" on Friday.