Just days after China banned access to Google, the Communist government has locked out a second major search engine, this time Altavista.

Although the government routinely blocks access to foreign news sites such as the BBC, its decision last week to block access to two of the biggest search engines has sparked protest from media freedom groups which are calling for a lift on the ban.

Requests for Google.com were blocked from Chinese servers at the start of the week and Altavista was locked out sometime last night.

A pair of students at the Berkman Center for Internet and Society at Harvard Law School have set up a website dedicated to the real-time testing of internet filtering in China.

Developed by Jonathan Zittrain and Benjamin Edelman, the site allows a user to input a domain name which is then queried via a Chinese web server.

If the request is denied the site is added to a growing list of websites locked out by the government.

The list is already in the thousands and, among the plethora of expected porn and human rights sites, includes such techie favourites as open source development site, Sourceforge.net.

Strangely, Yahoo, which uses Google as its search tool, is still accessible.