Google's plan to launch a censored search engine in China requires more "transparency, oversight and accountability," hundreds of employees at the Alphabet Inc. unit said in an internal petition seen by Reuters on Thursday.

Hoping to gain approval from the Chinese government to provide a mobile search service, the company plans to block some websites and search terms, Reuters reported this month, citing two people familiar with the matter.

Disclosure of the secretive effort has disturbed some Google employees and human rights advocacy organizations. They are concerned that by agreeing to censorship demands, Google would validate China's prohibitions on free expression and violate the "don't be evil" clause in the company's code of conduct.