Riot police flooded into the factory compound, broke up the strike and hauled away dozens of workers. Terrified by the violence, Shi was hospitalized with heart trouble, but with a feeble voice from her sickbed expressed a newfound boldness.

"We deserve fair compensation," said Shi, 41, who makes $4,700 a year at Cuiheng Handbag Factory in Nanlang, in southern China. Only recently, she had learned she had the right to social security funding and a housing allowance - two of the issues at stake in the strike.

"I didn't think of it as protesting, just defending our rights," she said.

More than three decades after Beijing began allowing market reforms, China's 168 million migrant workers are discovering their labor rights through the spread of social media. They are on the forefront of a labor protest movement that is posing a growing and awkward problem for the ruling Communist Party, wary of any grassroots activism that can threaten its grip on power.