BEIJING (AP) — More than a dozen human rights groups have sent a letter to Google urging the company not to offer censored internet search services in China.

The joint letter dated Tuesday calls on CEO Sundar Pichai to explain what Google is doing to safeguard users from the Chinese government's censorship and surveillance.

That follows a letter earlier this month signed by more than a thousand Google employees protesting the company's secretive plan to build a search engine that would comply with Chinese censorship, and calling on executives to review ethics and transparency at the company.

Google had previously complied with censorship controls starting in 2006 as it sought a toehold in the booming Chinese economy. But it faced unrelenting pressure from human rights groups and some shareholders to leave.