The report of a strike issued by China Labor Watch, a New York-based advocacy group, came weeks after Apple kicked off its largest-ever global rollout for the new iPhone 5 smartphone. Apple is already struggling with tight availability of the phones in stores, analysts say.

The labor group said 3,000 to 4,000 workers struck at Foxconn's Zhengzhou complex in central China on Friday afternoon, angered by over-exacting quality controls as well as demands they work through the week-long National Day holidays, which began on Monday.

But Foxconn Technology Group, which has its headquarters in Taiwan, denied the report and said the plant suffered only two brief and small disputes several days earlier.

"Any reports that there has been an employee strike are inaccurate," the company said in an emailed statement, adding that "there has been no workplace stoppage in that facility or any other Foxconn facility and production has continued on schedule."

Tensions have boiled over repeatedly in factories operated by Foxconn, the Taiwanese contract manufacturing giant that employs more than a million and makes most of the world's iPads and iPhones. Last month, thousands rioted at its Taiyuan facility in northern China, disrupting production for about 24 hours and underscoring the potential for labor unrest.

China Labor Watch said the dispute at the Zhangzhou plant arose over strict demands on product quality, which workers said they could not meet without more training.

In its response, Foxconn said the quarrels happened on October 1-2, and were "isolated incidents and were immediately addressed and measures taken, including providing additional staff for the lines in question."

Foxconn also said that employees who worked over China's National Day break did so voluntarily and were paid three times their usual hourly compensation, as demanded by law.

Foxconn Technology Group of Taiwan, the trading name of Hon Hai Precision Industry Co, is the world's largest contract maker of electronics for global brands such as Hewlett Packard Co, Nokia and Dell Inc.

Apple and Foxconn have come under fire for poor working conditions and wages at plants across China. In response, they have organized an audit of factory conditions, raised wages, improved safety and reduced overtime, among other measures.

Apple's chief executive officer Tim Cook visited Foxconn's vast complex on the far outskirts of Zhengzhou in late March.

(Reporting By Edwin Chan and Jonathan Standing; Writing by Chris Buckley; Editing by Richard Chang and Sanjeev Miglani)

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