The server concerned, at www.bbc.co.uk, provides access to most of the BBC's publicly-funded material, including BBC News.
The block means that Internet users in the capital cannot listen to the BBC's Mandarin broadcast in real audio or read transcripts of BBC Chinese Service News.
Also affected are the Web pages of the English language news and current affairs programme, East Asia Today.
The blocking appears to have begun within the last month. But the BBC's English Language news accessed from a different address, news.bbc.co.uk, does not appear to affected.
It is not clear whether other Internet providers around China, all of which are state-controlled, are also blocking the server.
An official of the state-owned Beijing Telecom, which runs China Net, has confirmed that www.bbc.co.uk is not accessible, but said he did not know why.
Lists of banned sites
Western experts in Beijing say the police submit lists of banned Websites to the Internet providers, who then block them.
But the government never publicly admits that it is doing so.
Banned sites include those maintained by Western news organisations like CNN, as well as several containing pornographic or dissident material.
It is possible that the BBC server has now been included because of its Chinese language content. In August, the server began providing Chinese news in audio format, making it possible for Chinese listeners to hear Chinese broadcasts without the interference that often affects the BBC's transmissions in Mandarin.
The BBC's Beijing Correspondent, James Miles, says the blocking of Internet sites is of limited effectiveness. With a little know-how, a user can quickly configure Internet software to access banned sites through what is known as a proxy server.
Users however have to register with the police and can be punished for retrieving information deemed pornographic or harmful to social order.
Net use growing
Internet use in China is spreading fast. Although only about 600,000 people were estimated to have access last year, experts predict the figure will lead to many millions by the end of the decade.
Our correspondent says China appears to be encouraging this, while at the same time trying to stem the tide of uncensored material that the Internet brings with it.
Country profiles
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(10 Oct 98 | Asia-Pacific)
HarperCollins apologises to Patten
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East Asia Today
Net Censorship Country Index
Internet Censorship in China
Human Rights and Democracy In China Information Centre
China Today
China.com
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