China's blocking of Twitter has failed to keep activists, journalists and others from using the messaging platform to connect with the rest of the world, said a study released Wednesday.

The study by Harvard University's Berkman Center for Internet and Society said it was not possible to estimate the number of Chinese Twitter users but said that "this alternative venue is enjoyed by various groups of people with diverse shared interests that gravitate towards three main areas: politics, technology, and entertainment."

The researchers said some "clusters" of people in China are defying government restrictions and using various tools to get around the so-called Great Firewall to use Twitter.

"For Internet users that reside in mainland China, Twitter offers access to news from around the world and a wealth of ideas and perspectives that might otherwise be unavailable there, as well as a platform for building online communities that is not under direct control of the government," the report said.

The report listed "36 clusters that focus primarily on three areas: politics, technology, and entertainment."

In the political arena, the researchers said the political group includes "journalists, lawyers, human rights activists, and scholars" who are free to discuss topics typically not permitted in China such as the Tiananmen Square protests, Tibetan and Uighur issues, political scandals, and pollution.

Other "clusters" of Twitter users include software and technology specialists, people who follow Apple products and services and others keeping tabs on anime, comics, and games.

But it noted that Chinese Internet repression "is clearly succeeding" and that Twitter remains a relatively minor phenomenon in the country.

"The proportion of the Chinese populace with direct access to the debates, communities, and shared resources on Twitter is relatively small, and the avenues by which such discourse might find its way into mainstream political discussion are severely constrained," the study said.

"The firewall between Twitter and the much larger social media platforms in China remains a formidable barrier."

The Berkman report said that while China's Internet filtering system is among the world's most sophisticated, determined Internet users get around it by using proxies or virtual private networks to mask a computer's identity and location.

"The government has never succeeded in blocking all circumvention tools, and doing so would be harmful to online commerce," the report said.

"However, jumping the wall entails investing time to identify and install tools that work and requires a level of technological sophistication... Circumventing Internet controls also implies a willingness to defy the government standards for acceptable speech and to take on any perceived risks associated with using circumvention tools."

The report said it remains unclear how many people in China have used circumvention tools. A previous Berkman Center study estimated that fewer than five percent of the online population uses these tools.