Microsoft's search engine Bing appears to be heavily censoring its Chinese-language search results across the globe as well as inside China, a cyber-monitoring group said Wednesday.

According to the group Greatfire.org, international Chinese-language Bing searches for topics deemed politically sensitive by Beijing return a drastically different set of results than English-language searches.

Censored search terms include the name of jailed 2010 Nobel Peace Prize winner Liu Xiaobo, the exiled spiritual leader the Dalai Lama and the 1989 Tiananmen Square massacre, it said.

"This is the kind of story that begets a Congressional hearing," the group, which tracks the vast Chinese online censorship apparatus known as the Great Firewall, said in a statement releasing its findings.

"We are 100% sure our findings indicate that Microsoft is cleansing search results in the United States to remove negative news and information about China," it added. "And they are doing this in every market in which they operate in the world."

A Microsoft spokeswoman did not immediately respond to a request for comment by AFP.

Bing is the second-most-popular Internet search engine in the US, with an 18.2 percent market share to Google's 67.3 percent in December 2013, according to Microsoft.

Tests conducted by AFP confirmed several of Greatfire.org's findings.

An English-language search using servers outside China for "Liu Xiaobo" returned a list of results from overseas sources including the Norwegian Nobel Committee, the New York Times, Encyclopedia Britannica and Wikipedia.

In a Chinese-language search of Liu's name, by contrast, six of the top ten search results were links to Chinese government and state-run media pages containing the same text -- a lengthy disparagement of Liu that compiles some of his more-controversial statements.

The first page of results from the same Chinese-language search using Google and conducted outside the country includes links to pages in Chinese from Wikipedia, the New York Times, German broadcaster Deutsche Welle, VOA and the BBC.

A Chinese-language Bing search for "Freeweibo", an anti-censorship tool developed by Greatfire.org, also returned a different list of results, with the Freeweibo Web site omitted from the search findings.