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Tencent and social media in China

7 December 2012 Last updated at 04:28 GMT

Social media firms are thriving in China where Twitter, Facebook and YouTube are blocked.

One of the highest profile of these homegrown companies is Tencent, which employs 20,000 people.

Rory Cellan-Jones took a tour of its purpose-built TV studios, where it broadcasts online programmes to big audiences who then comment via its Twitter-like Weibo service.

He also caught up with a leading social media campaigner, to find out the extent of online freedom of expression in China.