The case of a blind Chinese activist who sparked a diplomatic row with the United States is the latest illustration of the degree of power China's local authorities have -- and how it can backfire on Beijing.

Chen Guangcheng, who served four years in jail for his work in exposing abuses under China's "one-child" policy, sought refuge at the US embassy after his dramatic fight from de-facto house arrest last month.

But before he did so, he recorded a video appeal to China's Premier Wen Jiabao in which he accused local officials in his home province of profiting from his incarceration, and urged an investigation.

Officials were creaming money from the pay of the local men hired to guard his home, Chen said in the video, released on the Internet after he reached the safety of the US embassy in Beijing, where he remained for six tense days.

Interviewed during the diplomatic stand-off that ensued, senior US diplomat Kurt Campbell said he believed there were "many people in the Chinese government that feel that Mr. Chen has not been treated well" by authorities in eastern Shandong province.

It is unclear who in the central government was aware of the draconian treatment of Chen and his family, which included severe physical abuse, beatings and surveillance of his elderly mother and young daughter.

But the apparent decision to turn a blind eye to the treatment of a man who won worldwide acclaim for exposing abuses including forced sterilisations and late-term abortions backfired spectacularly with his very public flight to the embassy.

It was one of a number of recent cases in which local abuses of power in China have caused embarrassment for a government that has repeatedly stressed the importance of upholding the law and stamping out corruption.

Last December, residents of the southern Chinese village of Wukan staged a rare revolt against local officials who they said had been stealing their land for decades.

Like Chen, the villagers appealed to the national government to rescue them from the local officials who had made their lives a misery -- ultimately winning rare concessions.

"Things are changing in China. It is not like the time of Mao Zedong when everything under heaven was controlled by the Communist Party," said Li Datong, a leading social critic and former editor with the China Youth Daily.

"Today with rising living standards and the Internet there are so many social voices and so many demands complicating the situation. This is making it hard for the party to find different ways to handle social problems."

Some observers argue that it suits the Chinese government, under pressure over its rights record, to delegate the silencing of its challengers to local authorities who it can then claim acted without authorisation.

But the rise of the Internet -- China now has an online population of more than half a billion -- has made it much harder for the government to keep a lid on abuses of power, wherever they occur.

Earlier this year, the senior Communist party leader Bo Xilai was sacked as head of the southwestern metropolis of Chongqing over allegations of corruption.

Allegations of abuses of power by Bo had been made in the past, with no apparent repercussions.

But after his former police chief Wang Lijun fled to a US consulate with documents apparently providing proof -- an incident widely discussed on China's popular microblogs -- authorities were under pressure to act.

"Governance has become so much more complicated that the centre has less control of various levels of local governments. Local governments also have an interest in seeking as much autonomy as possible," said Joseph Cheng, political scientist and China expert at City University of Hong Kong.

"People also have much more access to information not controlled by the government."

Since the days of the emperors, the rulers in Beijing have faced difficulty exerting their will across China's vast landscape.

This challenge gave rise to the saying "the mountains are high and the emperor is far away" an adage that captured the impunity with which local officials could act due to their distance from Beijing.

"The capacity of the central government is one of the top concerns for Beijing and always has been," said Nicholas Bequelin, a senior researcher with Human Rights Watch and longtime China-watcher.

"But they worsen the problem by deliberately choosing to neutralise normal monitoring mechanisms such as civil society, and an independent media and judiciary, and so things will often get out of hand."