SAN FRANCISCO — Just over two months after threatening to leave China because of censorship and intrusions by Chinese hackers, Google said that it is closing its China-based Internet search service and instead direct Chinese users to a Hong Kong-based uncensored version of its search engine, which may get blocked in mainland China.

In a blog post, Google also said that it would retain much of its existing China operations, including its research and development team and its local sales force.

The stunning move represents a powerful slap at Beijing regulators but also a risky ploy in which Google — one of the world’s technology powerhouses — will essentially turn its back on the world’s largest Internet market, with nearly 400 million Web users and growing quickly.

“Figuring out how to make good on our promise to stop censoring search on Google.cn has been hard,” David Drummond, Google’s chief legal officer, wrote in the blog post. “We want as many people in the world as possible to have access to our services, including users in mainland China, yet the Chinese government has been crystal clear throughout our discussions that self-censorship is a non-negotiable legal requirement.”