China's web users are powering dissent

Tens of thousands of people have responded to Ai Weiwei's internet appeal for financial support

This week has seen an extraordinary surge in support for the artist and government critic, Ai Weiwei, from people around China.

By midday on Friday, one of his staff members says, 7.57m yuan (£740,000; $1.19m) had been donated to help the artist fight his tax demand from the government.

That is over a million dollars raised in little more than a week.

Without a doubt it is the appeals for help that have gone out over the internet that are behind this.

They have been posted by Ai Weiwei and others on China's microblogs.

More than 26,000 people have come forward.

Many of them are convinced the tax demand is an attempt to silence Mr Ai and they want to show their backing for him.

Famous for helping design Beijing's Bird's Nest stadium for the Olympics, Ai Weiwei has become of the most vocal critics of the ruling Communist Party.

Before his arrest the internet was the tool that he used to spread his thoughts.

He would spend hours avidly posting on Twitter or his Chinese microblogs.

Some of Ai Weiwei's supporters sent cash in envelopes, others used paper aeroplanes to launch it over a wall into his garden

Since he was held in secret detention earlier this year, then presented with his tax demand, he has been confined to Beijing and is officially banned from giving interviews.

But he has returned to the internet and that is what has enabled Ai Weiwei to reach out to those sympathetic to him.

The numbers responding seem to have surprised even the artist himself.

China's authorities have demanded that he pay 15.22 million yuan. To fight the claim he has to put down half that sum as collateral.

Not long after midday on Friday he had raised just about enough and announced that he would challenge the demand.

Without his internet fundraising it is almost certain he would never have had the cash to be able to keep up his defiance.

'Healthy internet culture'

A few hundred miles away near Linyi city, another campaign of internet-powered dissent is playing out.

The blind, self-taught lawyer Chen Guangcheng will spend his birthday on Saturday still confined to his home by local authorities.

The building is floodlit, all communication with the outside world severed.

Chen Guangcheng's supporters are using social media to co-ordinate their campaign

Chen Guangcheng spent four years in jail, convicted of organising a group to disturb traffic and damage property.

Most believe he was really targeted for highlighting official abuses like a campaign of forced abortions by local authorities.

Since his release more than a year ago, he and his family have been kept under unofficial house arrest, illegally, human rights groups say.

Chen Guangcheng's supporters will almost certainly use the occasion of his birthday to try, yet again, to visit him.

For weeks now they have been turning up in small groups at his village.

It is an unprecedented campaign by ordinary Chinese to reach someone the authorities have placed under detention.

All those attempting to get to him are intercepted by guards posted around the village - and many have been beaten up - but still they keep trying.

Again it is the internet and mobile phones they are using to co-ordinate and organise their defiance.

Last weekend, Communist Party officials called in senior executives from more than three dozen internet, telecommunications and technology companies to discuss controlling the flow of information on the internet.

They included the bosses of the main microblog services.

It was reported that they were urged to develop a "healthy internet culture."

And on Friday the General Administration of Press and Publications, the government department which regulates the print media, published new rules that ban news media from reporting any information on the internet unless it can be verified.

"Unverified reports are on an upward trend, and to a certain extent that has undermined the government's image, disrupted the information order, reduced the credibility of the media and brought a strong social response," the agency said.

Those new rules are designed to counter what officials say is the spread of "rumours" that can harm social stability.

That, of course, is a genuine concern for many governments.

But in two different parts of China, the supporters of Ai Weiwei and Chen Guangcheng are finding a new space on the internet to rally backers for their causes.

It is no wonder that the issue of how to control China's hundreds of millions of microblog users seems to be becoming more and more of a headache for the Communist Party.