A strike crippled production at a Japanese-owned electronics factory in this municipality on Thursday, expanding the country's industrial unrest pitting manufacturers against increasingly assertive workers.

Workers in green uniforms stage a sit-in protest at the main entrance of the Mitsumi Electric Co factory in Tianjin on Thursday, July 1, 2010. [China Daily via Agencies]

Tianjin Mitsumi Electric Co factory employees have been continuing a stoppage they began on Tuesday to win better wages and working conditions.

Handmade banners scrawled with employees' demands were hung from the factory's gate, and about 30 workers gathered in the rain near an entrance.

"Human traffickers are not welcome", read one banner at the gate. "We want a pay raise", and, "We want fair treatment", said other banners, some of which were several meters long.

"We're on strike because the factory has never increased our wages, but they keep increasing our workload. It's too tiring," a worker, who gave only her surname, Wang, told the Associated Press.

It was unclear how big a pay rise workers were demanding.

One told Xinhua News Agency earlier that he received just 1,500 yuan (US$220) a month despite working on Saturdays and putting in two hours of overtime every workday.

One employee, who declined to be named, told China Daily she earns only 700 yuan per month, which is below Tianjin's minimum wage.

Mitsumi Electric said the factory, which employs more than 3,300, had stopped production because "some of its employees demanded higher wages and improved benefits". The company said it was talking with the striking workers, and the "impact of the stoppage is limited at this point".

The factory is the latest high-profile target in the slow-burning but persistent labor unrest that has been rocking foreign-owned companies, often left vulnerable by their position in complex supply chains and a tightening labor market.

In recent weeks, striking workers have demanded higher wages from auto parts makers and other manufacturers, especially Japanese car parts companies operating in the south.

Workers, many of them migrants from poor villages, say their wages have not kept up with rising prices or the profits reaped by companies using China as a low-cost production base.

"These strikes show that workers feel more confident that the labor market is moving in their favor," said Li Changping, a former local official who studies rural issues and now works at an NGO's Beijing office.

"Part of it is that they feel left out of the wealth. But another part is they feel they have gained enough from rising wages that they can take a stand and demand a fairer share."

No specific law in China defines strikes as legal or illegal, but it is clear that authorities discourage such activity. However, those who have been taking the risks have been winning rewards.

Workers in South China's Honda engine gear factory won a 24-percent wage increase after a two-week strike. Those in Pingmian Textile Group factory in Central China also got a 25-percent pay hike after a two-week strike.

Liu Kaiming, the executive director of the Institute of Contemporary Observation, said the government should remain neutral whenever there is friction between management and workers.

"Local governments in South China generally realize that a crackdown is not the right reaction to a labor dispute," Liu said.

"It's one reason the Honda strike could end with an agreement on salary increases. Local governments in Central China should learn from this.

"The only thing local governments should do during strikes is maintain social order and help the two parities build a more efficient communication mechanism."

There also have been calls to urge Chinese labor unions to play a more active role in protecting workers' legal rights and improving their wages and working conditions.