San Francisco ? Google’s attempted detour around China’s Internet censorship rules was met with countermeasures Tuesday by the communist government, which blocked people on the mainland from seeing search results dealing with such forbidden topics as the pro-democracy movement.

China’s maneuver, as well as its public rebuke of Google’s decision to stop censoring searches for the government, rattled some of the company’s investors, advertisers and users.

The chief concern is whether Google poisoned its business in one of the world’s most promising Internet markets. One analyst critical of Google’s move predicted the maneuver will cause the company’s stock to fall by as much as $50 — or about 10 percent — in the coming weeks.

The stock fell $8.50, or 1.5 percent, to $549 Tuesday.

Last month, Google said it no longer felt comfortable complying with the country’s demands that it censor Web content deemed objectionable by the communist rulers. On Monday, Google began sending Web searchers in mainland China from the China-based Google.cn to Google.com.hk, based in Hong Kong. The former British colony has an open Internet, and Google is not legally required to censor results there.

But that end-run doesn’t prevent China’s government from using its Internet filters — known as the Great Firewall — to block some search results and Web sites from being seen in the mainland.