Activist Chen Guangcheng was jailed for public order offences

In just a few days China's leaders have shown once again that they will not tolerate dissent on issues they consider sensitive or embarrassing.

Earlier in the week blind human rights activist Chen Guangcheng was sentenced to four years and three months in prison.

The self-taught lawyer was well known in China for his outspoken campaigns to help poor rural farmers and the disabled.

But he gained international attention when he publicised claims that Chinese officials in the eastern province of Shandong were enforcing late-term abortions and sterilisations - in an attempt to control population growth.

That angered the Chinese authorities and Mr Chen was arrested and charged with destroying public property and disturbing social order. His supporters have always claimed the charges were fabricated.

Other Chinese rights activists who have campaigned for Mr Chen's release have been put under house arrest in Beijing, deported from there to distant cities, or gone into hiding.

Mr Chen's wife, Yuan, said officials restrict her movements to around her home village.

'State secrets'

Mr Chen's case has not been the only one to make the headlines this week. On Friday, a court in Beijing sentenced New York Times researcher Zhao Yan to three years in prison for fraud.

Mr Zhao was arrested in September 2004 (image: New York Times)

A more serious charge of revealing state secrets - which would have carried a much longer sentence - was dismissed.

Zhao Yan was arrested in 2004 after the New York Times correctly reported that China's former president, Jiang Zemin, was going to resign his last official position as head of the country's armed forces.

The United States and some human rights groups have repeatedly called for the release of Zhao Yan and Chen Guangcheng, claiming that their trials were politically motivated.

But China has ignored those calls - in fact these latest verdicts appear to be part of a growing clampdown by the Chinese authorities.

One of the most high profile cases is that of Hong Kong based journalist Ching Cheong, who reported on China for the Singapore-based Straits Times newspaper.

Earlier this year he was arrested while in the southern Chinese city of Guangzhou.

Mr Ching's wife said he had travelled there to collect secret papers linked to the former Chinese leader, Zhao Ziyang.

Ching Cheong has been tried on spying charges

Mr Zhao was ousted for opposing the suppression of pro-democracy demonstrators in Tiananmen Square in 1989. Beijing considered him an extremely controversial figure and he was still under house arrest at the time of his death in January 2005.

The Chinese authorities charged Ching Cheong with espionage and he was recently put on trial, although a verdict has yet to be announced.

Severe penalties

These cases are all reminders that while China may have experienced dramatic economic change in the past three decades, political reform is not on the government's agenda.

The government does not allow any challenge to its authority and keeps a tight rein on the media.

Beijing censors newspapers and television and has also invested considerable resources in trying to control what Chinese people see and read on the internet.

The authorities here regularly block access to material on the web that they consider pornographic or politically subversive.