The armies of migrant workers building Beijing's skyscrapers and Olympic venues are being bilked of wages and placed in dangerous conditions, Human Rights Watch said in a report released yesterday.

The report cataloged a variety of deprivations suffered by the estimated 1 million to 2 million migrant workers employed on construction sites before the Summer Olympics in Beijing: a lack of safety equipment, crowded and unhygienic dormitories, no medical care, arbitrary fines by bosses, and unpaid wages.

Human Rights Watch, an organization based in New York, said it interviewed an unspecified number of workers at nine building sites in Beijing in early 2007 and again this month. More than half said employers refused to pay their wages each month as required by Chinese law, and many had to wait until the end of the year for less pay than they had been promised, the group said.

"Despite years of government rhetoric, employers still cheat migrant construction workers of hard-earned wages," said Sophie Richardson, a lobbyist on Asian issues for the rights group.

The findings underscore the conditions rural migrants face as they provide much of the labor underpinning the economic boom. Their continued exploitation presents a challenge to the Communist Party chief, Hu Jintao, who has vowed to remedy their plight.

When asked about the report ahead of its publication, China's Foreign Ministry questioned the rights group's credibility.

"I believe that everybody is well aware that Human Rights Watch has some problem with its sight," Qin Gang, Foreign Ministry spokesman, said Tuesday.

A Chinese official said in January that six workers have died over the past five years working on venues for the Beijing Olympics.