by Hannah Vinter

Twitter has announced that it will begin selectively blocking Tweets in some countries.

"Starting today, we give ourselves the ability to reactively withhold content from users in a specific country -- while keeping it available in the rest of the world. We have also built in a way to communicate transparently to users when content is withheld, and why."

Twitter writes that it will withhold access to Tweets in certain countries "if we receive a valid and properly scoped request from an authorized entity". As an example of illegal material it names pro-Nazi content, which is outlawed in France and Germany.

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The number of new Internet users in China in the past three years exceeded more than the total number of Internet users in the USA today: that's a lot of people.

Despite this enormous amount of Internet users, the Chinese government has resolved to further increase online censorship. 39 firms have agreed to cooperate with this latest attempt to "curb rumours" and prevent the "spreading of harmful information", according to the BBC - including Baidu, a popular search engine, and Alibaba.

Google pulled out of mainland China in favour of Hong Kong during March 2010 due its objections to Internet censorship. Exercising this online control is now the job of the State Internet Information Office that was created in the same year.

According to the BBC: "Miao Wei, minister of Industry and Information Technology, called upon internet companies to strengthen their research and development to ensure better censorship of content."