There have been a series of labour protests
China is using repressive measures in tackling protests by workers, says Amnesty International.
The human rights group is calling on China to release people imprisoned for defending labour rights.
In a major report timed to coincide with the May Day labour holiday, Amnesty says labour unrest is growing in China.
But a Chinese Government spokesman dismissed the report, saying Amnesty International's reports often do not reflect the truth.
Millions upon millions of Chinese workers are experiencing huge upheavals in their daily lives as China transforms itself from a planned, state-run economy to more market-driven one.
This year there have been protests from the far south-west to the industrial rust-belt of north-east China where 30,000 people took to the streets of Liaoyang recently.
Clashes
Amnesty's report says more and more angry workers are staging demonstrations against layoffs, unpaid wages, poor working conditions, and management corruption.
A researcher for Amnesty's China office in Hong Kong, Dominique Muller, said the authorities' response has often been unnecessarily harsh and repressive.
Armed police have clashed with demonstrators. There have been detentions, and sometimes beatings and torture.
Labour activists can be imprisoned for up to 15 years for organising protests.
Amnesty also says many demonstrations go unreported because local authorities want to hide the extent of the unrest.
A spokesman for China's Foreign Ministry dismissed Amnesty's claims, saying "the organisation often issues irresponsible and incorrect reports that do not reflect the truth," adding that China was making progress in the area of human rights.
Poor conditions
China's leaders are now acknowledging the scale of the economic problems facing them. The Premier, Zhu Rongji, has said urban unemployment could double in the next five years, leaving 30 million out of work, which might undermine social stability.
The government's fears help explain its determination not to let workers form their own independent organisations or trades unions.
Amnesty International lists labour activists who it says should be freed from imprisonment, some of whom have been held since 1989.
It also warns that conditions for those in work are often atrocious. Some are made to do compulsory overtime, others are forbidden to talk during working hours or fined for going to the toilet too many times.
In the southern city of Shenzhen, Amnesty says every day an average of 13 factory workers lose a finger or an arm in industrial accidents.