Sources in China have reported that the English language version of Wikipedia is no longer blocked for internet users inside the country, after being unavailable for most of the past 18 months.

However, the Chinese language edition of Wikipedia remains inaccessible in China.

Most English language pages on Wikipedia became accessible late last week, according to bloggers across China, but some pages remained blocked by China's official firewall. 

These include references to 'sensitive' topics, such as Tibet and Tiananmen Square where a pro-democracy demonstration was violently suppressed in 1989.

Some other foreign news websites are also partly blocked. Google News appears to be dynamically blocked when certain keywords appear, but fully accessible at other times, and it seems that Wikipedia may now be monitored by the same automatic keyword detection software.

Other sites are blocked based on domain name. For example, news.bbc.co.uk is blocked while www.bbc.co.uk is not. 

Both the Chinese and English language versions of Wikipedia were first blocked in parts of China in 2004, and all Wikipedia sites have been blocked since late 2005.

The ban has been relaxed briefly on occasions, for example in November 2006, and then re-imposed. It is unclear whether this temporary lifting of restrictions has been deliberate, or caused by technical problems.

Many experienced internet users in China circumvent the so-called 'Great Firewall of China' by making use of proxy servers outside the country to read blocked pages.

While the country's internet authorities do not normally comment on the blocking of individual websites, restrictions are sometimes officially attributed to vaguely expressed 'security concerns'.

Chinese laws include very broad blanket restrictions on internet activity which effectively ban almost any behaviour that might be interpreted as hostile to the government.