"We are currently working with Chinese officials to get our full service restored to the millions of Chinese users who depend on Google every day," the company said in a statement.

For its part, China has defended its policy of maintaining tight controls on the internet.

Beijing routinely blocks access to thousands of sites with political or pornographic content deemed unsuitable for its citizens.

Popular choice

News of the ban on Google emerged on Monday.

Not everyone should have access to this harmful information on the internet

Kong Quan, foreign ministry spokesman

The site was repeatedly inaccessible when tested by BBC News Online using a system developed by researchers at the Harvard Law School.

Google has become popular in China because of the simplicity of its pages and the ability to run searches in the Chinese language.

In various online forums, Chinese surfers criticised the ban saying they used the search engine for research, not politics.

Managing the net

China has made no official comment on the ban on Google.

But when asked why Beijing was blocking the search engine, a foreign ministry spokesman defended state controls on online access.

Google has always been committed to providing our users with the most open access to information possible

Google statement

"Obviously there is some harmful information on the internet," said foreign ministry spokesman Kong Quan.

"Not everyone should have access to this harmful information on the internet. The whole world now is exploring a way to manage the Internet and China is also working on this."

The Beijing Government is keen to promote the use of the internet for business in China. But it also tries to maintain strict controls over what its citizens read on the net.

Analysts say this is the first time China has blocked a search engine.

"Google has always been committed to providing our users with the most open access to information possible," said the company.

The search engine is one of the most popular sites on the internet, receiving more than 150 million hits a day.