A 16-year-old Taiwan singer with a South Korean girl band inadvertently shot to the top of Taiwan's election agenda on Saturday after she publicly apologized for holding a Taiwan flag, prompting anger in Taiwan as it voted for a new president.
China and Taiwan traded accusations after Chou Tzuyu, the only Taiwanese member of Twice, released a video late on Friday in which she said she feels proud to be Chinese and that there is only one China, after she held the flag on a television show.
The video, showing Tsuyu in a plain black sweater apologizing and bowing, quickly went viral, some media reports said.
The issue is sensitive in self-ruled Taiwan - and could play into how people vote - where many people resent China's claims on their island and feel proud to be called Taiwanese rather than Chinese. Taiwan media gave the issue blanket coverage.
Taiwan presidential front runner Tsai Ing-wen, from the pro-independence opposition Democratic Progressive Party (DPP), told reporters as she cast her vote that Chou's video had seriously hurt the feelings of Taiwan's people.
"We should all take the same attitude and make it clear to the international community that holding a Taiwan flag is a legitimate expression of national identity," she said.
In Beijing, China's Taiwan Affairs Office shot back that the spat was being "used" by certain political forces in Taiwan to "stir up the feelings of people on both sides of the Taiwan Strait".
"Compatriots on both sides should be on high alert over this," it said, in a statement carried by Chinese state media.
Defeated Nationalist forces fled to Taiwan in 1949 at the end of the civil war. China still considers Taiwan a rebel province and has warned repeatedly it will never tolerate formal independence.
Artists cannot afford to upset China's ruling Communist Party or risk being shut out of its massive market.
On Saturday, Chou was the 5th most searched topic on Weibo, China's answer to Twitter, with many people saying she did the right thing.
"It's terrible they tried to force her into supporting Taiwan independence," said one Weibo user.
JYP Entertainment, the South Korean management company behind Chou's group, did not answer calls seeking comment.
But in a statement on its Chinese microblog it said it was sorry for the "harm caused to our Chinese friends" and promised the company would "respect other nation's sovereignty".
On the streets of Taipei, there was anger at China and suspicion JYP forced Chou's statement on her lest the band be banned in China.
"She's just being used," said 70-year-old Liu Chao-chih. "We're proud to be Taiwanese. No one should be forced to say they're Chinese. We're not."