Internet experts have warned that censorship in China, Iran, Saudi Arabia, Cuba, Myanmar and North Korea could threaten the growth of some social networking companies.

While the different countries are filtering or blocking access to Internet sites they deem dangerous, Silicon Valley companies in California, such as Facebook, Twitter, YouTube and Google are concerned their growth will be stifled.

The affected companies provide news, information and social access.

The named governments regard Internet information as a high security priority, because of the political content which can be transmitted.

China alone has 384 million Internet users, who are seen as part of a potentially rich growth market.