Apple said Monday it would investigate claims that an iPhone electrocuted a Chinese woman who was making a call while charging the device.

The case drew attention -- both sympathetic and sceptical -- after a woman in the western region of Xinjiang wrote about the death of her 23-year-old sister Ma Ailun on China's popular microblog service Sina Weibo.

"We will fully investigate and cooperate with authorities in this matter," said Apple's Beijing-based spokeswoman Carolyn Wu, offering condolences to the family.

The state news agency Xinhua said on Sunday that local police had confirmed Ma died of electrocution but "have yet to verify if her phone was involved".

Ma's sister warned others not to talk on their iPhones while charging them, saying on Weibo on Saturday: "Hope Apple can give an explanation!"

"What a shame, to pass away like this," she wrote of her sister.

Weibo users expressed concern about the potential danger but also questioned if it was real.

"If the accidents are real, let's be more careful when using our mobiles," one person said, but added: "Is someone trying to smear Apple?"

China is Apple's second largest market and its iPhones and other products, many of them made in the country, are highly popular.

But the company came under torrents of criticism from state media in April for alleged "arrogance" and double standards, prompting an apology from chief executive Tim Cook.

The People's Daily, a mouthpiece of the ruling Communist Party, slammed the firm for five days in a row, urging consumers to "strike away Apple's unparalleled arrogance".

Chinese consumers had to pay about $80 for new back covers for their devices, even though they were free in other markets, local media reported at the time.

In a Chinese-language letter, Cook said "we sincerely apologise for any concerns or misunderstanding".

Apple had "many things we have to learn" about operating in the country, he added.