Thousands of Chinese workers protesting over compensation and job security at a Sanyo Electric Co Ltd plant clashed with police in southern Shenzhen, media said on Monday, the latest outbreak of labor unrest in China's manufacturing hub.

About 4,000 workers protested over the weekend at the Sino-Japanese joint venture, the Chinese-language Oriental Daily reported. Sing Tao Daily and the website put the number at over 3,000.

The website said police arrested four people after clashes with police in Shenzhen, next to Hong Kong.

Sing Tao Daily quoted an employee as saying that workers feared they would not receive any compensation after Sanyo and Panasonic Corp <6752.T> integrated their businesses this month.

A Panasonic spokesman said in Tokyo said there had been a strike on Saturday at a Shenzhen factory that makes parts for audio speakers, but that production had returned to normal on Sunday.

The strike was sparked by the integration of the two companies, said spokesman Akira Kadota but he added that the exact nature of workers' demands was not clear, though the company was continuing to negotiate.

No impact was expected on clients from the stoppage at the factory, which employed about 3,400 people as of December 2010.

Hong Kong media also reported that about 2,000 workers protested at a factory in Jiangxi province owned by Changhe Auto, a unit of Changan Auto.

Workers were concerned about compensation and benefits after the parent company sold off Changhe's brand, the Oriental Daily said.

Changhe was not immediately available for comment.

Thousands of workers at factories of foreign companies in China have gone on strike or staged protests over the past year or so, demanding more pay and compensation.

The labor unrest disrupted production of shoe and apparel facilities in Guangdong province and watch, sportswear and electronics plants in the south and west.

In December, nearly 1,000 workers at a Japanese-owned factory in Shenzhen staged protests, demanding compensation based on their length of service after a change in factory ownership, media said.

(Reporting by Lee Chyen Yee in Hong Kong and Isabel Reynolds in Tokyo; Editing by Ken Wills and Edwina Gibbs)