Illegal workers from Vietnam and other Southeast Asian countries are migrating to the Yangtze River Delta region to work in China's booming factories.

Along the Sino-Vietnamese frontier at the Guangxi Zhuang Autonomous Region, a Vietnamese migrant can simply walk across the border into China, provided they evade border guards, according to the Yangtze Evening Post.

And with the purchase of a bus ticket, migrants can head to China's big cities.

Some 28 illegal migrants from Vietnam worked as cheap labor at a Zhuji City-based textile factory in Zhejiang Province for almost a year until they were discovered and repatriated.

"It never occurred to me that I was working with a group of foreigners," a factory worker surnamed Li told the newspaper.

"It's the first time I have heard of foreigners coming to China to work as cheap labor."

The factory was fined 20,000 yuan (US$3,009) by the city government.

The factory's chief manager, surnamed Yang, told the newspaper that they hired Vietnamese workers due to labor shortages.

These have been created partially by the economic upturn following the financial crisis, which has prompted factories to hire workers.

Yang said when he was on business in Vietnam, workers complained about low salaries and he persuaded them to come to work for him by guaranteeing better wages.

Vietnamese workers were paid 1,000 yuan each per month at Yang's factory, compared to the equivalent of 400 yuan in Vietnam for the same work, said the newspaper.

Yang told the newspaper that the Vietnamese labor agent company he had used sent 400 Vietnamese to China illegally every year.

Those laborers used to work at the Pearl River Delta region, but with the rise of labor-intensive enterprises, the workers are now swarming to the country's Yangtze River Delta region.