Beijing (AsiaNews/SCMP) – Wang Binyu, a 27-year-old migrant worker from Gansu has been condemned to death for killing four people who had not paid him for five months. Wang worked for more than a year on a construction site in

 Ningxia, in Shizuishan: he said he killed his supervisor and three of the supervisor's relatives in a fit of rage.

Wang hopes his story will serve to finally draw attention to the necessity of protecting the human rights of migrant workers like himself. The condemned man spoke out to a Chinese government press agency, saying the homicide took place on 11 May when he went to the head of the construction site to get 5,000 yuan (around 502 Euros) which were owed him. The employer called the supervisor and three of his relatives to send Wang away and they beat and insulted him. Enraged, Wang took out of a knife and killed the men. "I really could not stand any more at that moment. I'd had enough of them," Wang said.

He turned himself in to police later that day and was sentenced to death by a local court in June.

Protests about unpaid wages have also been taking place in a construction site set up for the Olympics in Beijing in 2008. Around 500 workers of a Nantong firm have refused to leave the site of the National Conference Centre after their client decided to change construction firm. The workers have also prevented 300 of their colleagues belonging to the new firm (of Sichuan) from starting work. "We have not received a penny after three months of work," said a manager of the first firm. "How can our workers go home?"

Such cases are emerging amid a campaign launched by the government to resolve the widespread problem of back payments owed to migrants, especially workers in the construction industry (around 70% of the total). The campaign was launched in 2003 but it came to national attention last year during deliberations of the National People's Congress meeting last year when Premier Wen Jiabao pledged that the issue of outstanding wages in the building sector would be "generally resolved" by 2007. The commitment meant any money owed before last year would be paid by February this year, and a system would be put in place to stop it mounting up.

According to government media, around 33 billion yuan (more than 3.3 billion Euro) in back pay accumulated before last year had been paid to migrant workers. But new cases continue to occur.

"I know there are policies to protect our rights, but people at the local level don't execute [the policies]. Our rights still can't be protected," Wang said.  "We are working at height and can fall and die in an unguarded moment. Do you know how many migrant workers died while building those big towers?"

Du Yang, a labour economist at the Chinese Academy of Social Sciences, said ensuring migrant workers got paid on time came at a price for the government.

"For every 1,000 yuan in overdue wages collected, the government might have to spend 3,000 yuan," Mr Du said. "It is also an issue of whether there are enough people to supervise and regulate construction sites." Mr Du said some employers would withhold wages – instead of giving them to workers – if they knew they were not likely to get caught.

In China, there are around 150,000 million such workers, compelled by extreme poverty in rural areas to move to urban centres to work. Migrants are forced to work for very low wages – even by Chinese standards – and for inhuman hours: they have become the main work force in construction and manufacturing sectors.