SHENZHEN - Police in the southern boomtown of Shenzhen said Wednesday that they have arrested nine people who failed to pay a significant sum of wages to their employees.

They were arrested in a crackdown, co-launched by the city's police and the human resources and social security bureau, in the latest move by the city to beef up the protection of migrant workers.

The 50-day campaign started on December 7, just ahead of the New Year and China's traditional Spring Festival, a time when most of the country's migrant workers in cities plan to claim their unpaid wages before returning to their hometowns.

The nine employers, eight in police custody and one out on bail, have allegedly fail to pay over 8 million yuan ($1.27 million) to more than 780 workers, said the statement.

In addition to the crackdown, police also talked to many employers and warned them not to withhold wages, it said.

China has taken various measures to ensure that wages for migrant workers are paid.

In February, the Standing Committee of the National People's Congress passed an amendment to the Criminal Law to stipulate that malicious wage default is a crime, and employers who intentionally withhold pay face up to seven years in jail.

In 2008 and 2009, amid the global financial crisis, the government enhanced efforts in cleaning up defaults, retrieving wages of 8.3 billion yuan and 8.9 billion yuan, respectively. Last year, the government retrieved 9.9 billion yuan for the workers.