Updated with Foxconn denial at the bottom..

With delays and retail shortages reported by retailers and carriers worldwide for the launch of the iPhone 5, reports from today claim that pressure on Foxconn employees in Apple’s assembly factories has lead to a strike among thousands of workers. China Labor Watch (via Gizmodo) reported today that 3,000 to 4,000 workers at Foxconn’s Zhengzhou plant went on strike earlier today due to overtime demands and lack of training. According to the report, Foxconn has “raised overly strict demands on product quality without providing worker training for the corresponding skills.” This had led to fights between supervisors and workers, and ultimately the strike:

The quality control concerns were apparently related to issues users have reported with scratching on the exterior of the iPhone 5:

Last month, Apple Marketing Senior Vice President Phil Schiller responded to a customer regarding the issue. He called the scratches and chips “normal” for any aluminum product.

It is unclear at this point, how the strike might affect supplies of iPhone 5 going forward. However, late last month, Apple continued experiencing shortages and delays for the rollout of the device to 22 new countries. While yield issues with the device’s in-cell display technology was originally thought to be behind production delays, reports in September confirmed supplier Sharp began mass production after weeks of delays. China Labor Watch said today “multiple iPhone 5 production lines from various factory buildings were in a state of paralysis for the entire day.”

Update: Reuters got a statement denying the stoppage from admittedly biased Foxconn:

Foxconn said the quarrels happened on October 1-2, 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.

But China’s official Xinhua news agency quoted a government spokesman in Zhengzhou as saying some 100 quality inspectors at Foxconn refused to work for an hour on Friday after one was allegedly beaten by workers irate over the inspection demands.

“The instruction to strengthen quality inspections for the iPhone 5 was given by Apple Inc. following multiple complaints from customers regarding aesthetic flaws in the phone,” said the unnamed spokesman for the industrial zone that holds the Foxconn plant. Apple has not commented on the incident.