Around 1,000 workers at a Chinese plant that manufactures components for Apple and IBM downed tools this week in protest against enforced overtime, a rights group has claimed.

The disgruntled staffers - about a third of all employees - at Jingmo Electronics Corporation (JEC) in south China's industrial district of Shenzhen held a one-day strike on 22 November.

The authorities dispatched several hundred police including riot officers to disperse the workers as they moved off-site and blocked a national highway.

China Labour Watch (CLW) said: "the motivation behind the strike was the factory’s decision to make workers work nightly overtime."

It claims that employees had been asked to work from 6pm to midnight and sometimes 2am on top of the usual four to four and a half day shifts from 7am to 11.30 or 1pm to 5pm.

CLW said staff "commonly worked anywhere from 100 to 200 hours of overtime a month" but the factory refused to let them put the hours in at the weekend because under Chinese labour law JEC would have had to double the wages.

On top of concerns about overtime, the workers were aggrieved about the high rate of workplace injuries, mass layoffs of older staff, the lack of benefits and the abusive treatment by bosses, the not for profit organisation claimed.

Following the strike, the factory has agreed to cut the average overtime hours and open its doors on a Saturday.

"China Labour Watch calls upon Apple, IBM and the other clients of this factory to assume responsibility for these workers’ dissatisfaction and work with the factory to improve the working conditions in the factory.

"We particularly urge Apple to take responsibility, as there are more than 300 workers working on the Apple keyboard assembly line," it added.

Working conditions at factories in China have been placed under the spotlight on several occasions in recent years, brought into focus by the suicides at Foxconn which produces products for Apple and HP.