Although Twitter has been blocked in China since it was used to spread images and messages of deadly Uyghur riots in Xinjiang in July 2009, millions of Chinese Internet users have found a way around the blockage.

They have their own version of Twitter, called microblogs, which are offered by China's major Internet portals. Indications are that while the authorities are nervous about the messages, which can be 140 characters long, and have shut down some threads, mostly they have left them alone. Internet users can repost the threads after they have been censored, and the followers of that tweet can forward the post within a second, creating a huge Internet traffic.

The number of microblog users in the country has increased to 53.11 million, making up 13.8 percent of China's Internet users last year. A recent report by Shanghai Jiaotong University said 11 of 50 major events triggering hot public debate were first made known to the public by microblogs. Analysts believe microblogging plays an important role in raising civic awareness and exerting pressure on officials, even though – if the authorities demand – sensitive materials will still be deleted.

Luk Wah, a postgraduate student in Beijing, said she previously only used the Internet for e-mails or to watch video clips or news. She seldom writes on the Internet, she said, because she believes she has nothing special to share with others. But she opened a microblog in Sina, China's major Internet portal, two weeks ago, after her father had been detained for two weeks in Liaoning Province and her mother went missing.

Her father was involved in an economic dispute against the local government, and the local court ruled that the father should be compensated. But when he went to the local government office to demand compensation, officials detained him, allegedly because he had caused a disturbance.

"I am desperate and want your help," she wrote, leaving her mobile phone number.

"I am not a computer-obsessed woman. I believe communication via the Internet is something only fashionable people do," she told Asia Sentinel. "I used other methods to deal with my father's case, but all efforts were futile. I was so desperate and I did not know what to do. I didn't even know what a microblog is. But I needed someone to help."

The attention generated was beyond Luk's expectations. She received dozens of phone calls from strangers asking about her father's condition. She was thankful to the microbloggers after her father was released Friday.

"I almost want to write a thank you letter to Sina," she said.

Wang Sixin, a professor at the Communication University of China, said the easy-to-use feature of microblogging enabled many people who were reluctant to discuss public affairs to express their views.

"Unlike blogs or other online forums, you don't need to write long articles. Only 140 characters or a picture is enough," he said, adding that the other functions of microblog, which allow users to forward and comment on others' posts enable Internet users to interact with each others, forming a large group.

When negotiations with officials fail, or when they failed to attract the attention of mainstream media, or when the mainstream media are banned by the propaganda machine from reporting certain topics, the Internet users just write 140 words in the microblogs. The impact of such a little thread can be unimaginable, and undesirable to officials.

Zhong Rujiu, a 22-year-old sales in Yihuang county, Jiangxi Province, is constantly updating the situation of her sister and mother in her microblog, which has about 30,000 followers.

Zhong's family attracted nationwide attention on September 10, 2010, when more than 100 officials forced them to accept a deal to demolish their homes to make way for a transportation terminal. The negotiation broke down, and Zhong's mother, 59, sister, 31 and uncle, 79, set themselves afire to express their anger. The uncle died, and the two other women survived.

When Zhong and her other sister went to go to Beijing six days later to petition to central authorities, officials followed them to an airport in Jiangxi. The two fearful women locked themselves inside an airport toilet for 40 minutes, during which they use their mobile phones to update their conditions to journalists and other Internet users. Zhong's brother said in his own microblog that he was under house arrest.

One of the reporters, Deng Fei from the Phoenix Weekly, posted more than 20 threads over the next few hours about the situation faced by the sisters. Each of these threads were forwarded by hundreds of Internet users.

The saga ended up with the removal of several officials, including the county head and the deputy party secretary of the county construction bureau. The deputy head of the county public security bureau was also reprimanded.

Officials are getting more fearful about the Internet. A survey of 300 officials and ordinary citizens conducted by the People's Forum magazine last April showed that 47 percent of officials afraid of being monitored by Internet users, most of them are at county level.

Zhang Hongfeng, a deputy head of a district level environment bureau in Hunan Province, believes microblogs reflect the strong desire for citizens to participate in public affairs, and that is a headache for some governments.

Zhang is considered an open-minded official because he often writes on his blog about problems faced by ordinary people, and he participates enthusiastically in his microblog over in the Yihuang self-immolation incident.

"The microblog and the Internet changes how the government operates," he said. "The government cannot handle problems in black box operations. They have to be transparent and subject to higher public scrutiny."

Another illustration of the powerful impact of microblogging is Guo Yuanrong, who was confined to a mental hospital for 14 years after he accused officials of corruption. When friends and family failed to get wide attention after talking to local government and the media, they posted a story in an online forum that said Guo's daughter was willing to "marry to or be a slave of" the man who could save her father.

The gist of the story was spread through the microblog, immediately drawing the attention of the media and leading to rampant discussion over the wrongful detention. The local government ultimately was forced to release Guo -- although he has no such a daughter willing to be a slave.

Wang, the Communication University of China professor, says he expects more people will use microblogs to express grievances along with the economic development of China, when people are more frustrated with officials' lack of response to their problems, especially land acquisition.

"Only when their problems are solved will people stop using microblogs or other media to express their grievances," he said. "Microblogs enrich the interaction of people facing problems with the outside world. It is a platform for these people to get attention and criticize the government."

The microblog may send a chilling effect to officials because very often it is used to show distrust to the government. When Qian Yunhui, a former village chief of Zhejiang Province, was crushed to death by a truck on December 25, an Internet user wrote in his microblog that Qian was murdered by the government.

The thread attracted attention of others, leading to the discovery that Qian had helped villagers petition the government over land acquisition issues. Many Internet users quickly concluded that Qian was ordered to be crushed because he had offended the authorities.

Zhao Lihua posted two articles on her microblog written by Qian accusing local officials, and the threads were followed by more than 20,000 and 6,000 people.

The government concluded the death was merely a traffic accident, and ruled out the possibility of murder, but the microbloggers quickly dismissed the findings.

The impact of the 140-word thread is often magnified when renowned journalists and opinion leaders join the discussion. In Qian Yunhui's case, the local government first remained silent, but was later forced to convene a press conference when the microblogs were full of sympathy for Qian, and investigative reporters such as Wang Keqing, who broke a story that hundreds of kids in Shanxi Province were affected by a problematic vaccine, devoted their attention to the incident.

Wang said he believes the microblog will help to shape the country's political and power structure.

"Some officials may be shivering and are under immense pressure," he said. "When problems are exposed, authorities at higher levels may exert pressure to fix them. The lower officials cannot hide the problems anymore."

Both Wang and Zhang, the district level deputy environment chief, said it is more difficult for the propaganda machine to censor microblogs than normal blogs and online forums.

"It is not controllable," Zhang said.

However, there are incidents of censorship. Texts in support of jailed Nobel peace laureate Liu Xiaobo and images of the empty chair that represented Liu's absence in Oslo, Norway, were deleted after they were posted.

The microblogs of Wu Danhong, an assistant professor at the China University of Political Science and Law who writes under the alias Wu Fatian, have been blocked and deleted. Wu said he was told by a Sina manager that it was a decision "from the top" because Wu's posts had dealt too much with politics.

A reporter from Youth Times approached Sina, and was told that Wu had spread messages attacking the government. Although Wu re-opened the microblogs through different user names, they have been blocked sporadically.

The government may also attempt to silence the Internet activist Chen Yonggang, who created the fake daughter story to save Guo Yuanrong from the mental hospital, who said officials had told him that they are well aware of his wrongdoings.

Fearful of the repercussions, Chen said he may not use the Internet to express grievances of others. Although he said he would help people negotiate with the governments, he will not pursue their cases further through the Internet if the officials refuse to take remedial actions.

"If I damage the big environment, it will be difficult for me to survive," he said.