A labor rights group marked the launch of Apple's latest iPhone with a report accusing one of the smartphone giant's Chinese suppliers of exploiting factory workers.
Hong Kong-based Students and Scholars Against Corporate Misbehavior (SACOM) say Lens Technology, which makes touchscreen glass, used forced overtime, withheld wages and risked workers' health after a months-long investigation into three of its factories.
Company founder Zhou Qunfei, herself a former factory worker, became China's richest woman after Lens Technology's debut on the Shenzhen stock exchange in March.
As the iPhone 6 went on sale in markets including Hong Kong, Japan and mainland China on Friday, SACOM called for Apple to "apply immediate measures to rectify exploitations in its supply chain".
"We urge Apple Inc. to fulfill its corporate responsibility... to give workers a workplace with dignity and respect," a statement said.
The allegations involve employees working for a month without a day off, wages being withheld for weeks and the company failing to pay social security.
"Dust, noise, polluted water and chemical substances are common problems on the shop floor," it added, with management "ignoring if workers were well-protected".
It sent undercover workers into factories, as well as interviewing workers off-site.
SACOM was to deliver its new report on Friday to Apple and Lens Technology, which is based in the southern Chinese province of Hunan.
Around 10 protesters gathered outside one of Apple's largest stores in Hong Kong on Friday morning, holding giant phones with the slogan "Throw Away The Bad Apple".
But the supplier denied any wrongdoing, saying overtime is not mandatory, and that it strictly limits overtime to two hours a day and workers take at least one rest day per week.
It also denied failing to pay social security and said it carries out regular inspections of the working environment.
"Lens Technology is a listed public company and has always complied with the laws and regulations, as well as strictly following the parameters set by our clients," the company said in an email to AFP.
"During peak season there is indeed overtime but it is not forced... Many employees actually raise their hands to work overtime to earn more."
The hundreds of customers who had pre-ordered one of the new phones were largely oblivious to the allegations.
"I think bad conditions happen to all brands," said James Leung, 30, who was waiting to pick up a rose-gold phone for his wife, which he said cost him HK$5,000 ($645).
"For me, I need a phone, so I'll get a new phone."
Lens Technology also supplies Samsung and other leading tech firms. SACOM spokeswoman Liang Pui-kwan said the group was not only targeting Apple.
"But Apple is the richest and has the biggest ability to make change and bring the industry forward," she said.
Apple was not immediately available for comment.
The iPhone 6S features a new "3D Touch" feature that allows users to differentiate between a light touch and a harder tap, with the phone reacting differently to each.
In Asia-Pacific, the phone was launched in Australia, China, Hong Kong, Japan, New Zealand and Singapore on Friday.