BUNDANG, Korea, Republic Of -- When Lee Kyung Eon and her friend recently scrapped plans to go to Japan for summer vacation, they paid a $135 penalty for cancelling their plane tickets, joining a growing campaign in South Korea to boycott Japanese goods and services.

"We intended to do something that doesn't help Japan, even (it's only) a little thing," said Lee, a 26-year-old office worker in Bundang city, just south of Seoul. "Many people told us we did something really good."

A widespread anti-Japan boycott has gained ground in South Korea since Tokyo on July 1 tightened control of exports of three chemicals used to manufacture semiconductors and display screens -- key export items for South Korea. The boycott could worsen as Japan is expected to expand its export curbs to other materials as early as Friday by removing South Korea from a list of countries granted preferential trade status.

There have been anti-Japanese rallies in South Korea over the Japanese trade curbs, but none has yet turned violent. Two men in their 70s have set themselves on fire in an apparent protest against Japan. One died and the other, who set himself ablaze on Thursday, remained in critical condition.

South Korea accuses Japan of retaliating over local court rulings last year that ordered two Japanese companies to pay compensation to former Korean employees for forced labour during Tokyo's 1910-45 colonization of the Korean Peninsula. Japan has denied that, saying its action was taken out of national security concerns.

Some question whether the boycott, mostly targeting consumer goods, can really hurt the Japanese economy as a majority of Japanese imports are parts and materials used in TVs, smartphones, semiconductors and other electronic products that South Korea exports. They worry the boycott could only aggravate the animosities as it may trigger a backlash from Japan.

But others say the campaign exposes the bitter resentments many South Koreans still harbour against their former colonial ruler. A recent survey suggested 80% of South Koreans are reluctant to buy Japanese products.

Angry South Koreans have taken to Instagram and other social media, posting videos on their cancelled Japan-bound plane tickets, sharing information on which Japanese companies operate in South Korea and expressing their support for the boycott.

There have been some consequences.

HanaTour, the largest travel company in South Korea, said a daily number of reservations for Japan trips has dropped to about 400-500 from 1,000-1,200 late last month. Other tour agencies have reported similar or lower booking figures for Japan tours.

Last year, about 7.5 million South Koreans visited Japan, making it the most popular destination. The state-run Korea Tourism Organization said it has no data on how many South Koreans travelled to Japan this month.

At hypermarkets and 24-hour convenience stores, the sales of Japanese beer have nosedived. Beer is the most popular among Japanese products. For example, at E-mart, the largest retailer in South Korea, the sales of Japanese beer from July 1-24 declined by about 38% from a month ago. Tens of thousands of small supermarkets and convenience stores across South Korea have stopped selling Japanese beer and other products altogether.

Customs officials said the imports of Japanese cars from July 1-20 was estimated at about $46 million -- a 32% decrease from the same period last year. Fast Retailing Co., which operates Uniqlo, was forced to apologize last week after inviting criticism in South Korea over the remarks by one of its executives that the boycott won't last long.

"Even without Japanese products, there are still lots of things to sell, and customers aren't actually looking for Japanese products," said Dan Kil-su, owner of Seoul's Heemang supermarket who removed all Japanese products from shelves on July 5.

One of the store's regulars, Chon Jong Lee, supported Dan's action. "I think I originally had stronger anti-Japanese sentiments than other people. I have really bad feelings about them," Chon said.

Past anti-Japanese boycotts didn't last long, but some say Japan's expected new exports limits could amplify the crisis.

"The boycott isn't helpful in resolving the conflict, though some may feel cool by venting their anger at (Japanese companies)," said analyst Lee Sangho at the Seoul-based private Korea Economic Research Institute. "If public sentiments (in both countries) get worse, we may see a situation that spirals out of control."

Lee Myon-woo at the private Sejong Institute near Seoul said the boycott will likely have a limited effect on the Japanese economy. He also said that the lower number of South Korean tourists to Japan will likely be compensated by Chinese and other foreign visitors.

Some worry the boycott will eventually undermine the South Korean economy because a withdrawal of Japanese companies would lead to their South Korean employees losing their jobs, while fewer tourists would incur losses for South Korean tour agencies.

Ahn Kyung-su, a researcher in Seoul who plans to visit Tokyo this weekend for his summer vacation, called the boycott "anachronistic" and illogical. "Our TV stations mostly use Japanese-made cameras. So do we have to stop watching their programs?" Ahn asked.

Japan hasn't yet reported a similar eruption of anti-South Korean sentiments. K-pop super stars BTS' four concerts in Japan this month reportedly drew a total of 210,000 spectators.

At Shin-Okubo, a major Korea Town in downtown Tokyo, business was as usual this week, with many Japanese looking for K-pop music, Korean food, cosmetics and other merchandise.

Misaki Toguchi, a 14-year-old junior high school student from Saitama, north of Tokyo, said her devotion to BTS and K-pop is unshakable despite the news of the disputes. "There is absolutely no change; I still really like Korea," Toguchi said.

"These (disputes) are something that only top officials in the government are doing. I don't think there is any impact on ordinary people like us," said Keiko Katsumata, a part-time worker who was in Korea Town with her friend.

The two countries are closely linked to each other culturally. Many South Koreans like dining at Japanese restaurants, watching Japanese animation films and travelling to small towns in Japan.

Speaking before a large placard hung at his Heemang store that partly reads "We are not selling Japanese products," Dan said his family cancelled their plans to go to Mount Fuji for holidays this summer. "In fact, Japan has been a country that I've wanted to visit," he said.

Lee Kyung Eon, who decided to go to Taiwan with her friend in August instead of Miyhazaki, Japan, said she also used to enjoy Asahi beer, sushi, soba and other Japanese foods. She said she's already visited Japan twice.

She admitted there have been ups and downs in her feelings toward Japan, saying she had a good impression following her trips to Osaka and Fukuoka before anti-Japan sentiments resurfaced in her mind when the two countries fought over history.

"The level of my hatred against Japan is now at one of the worst points in my life," Lee said.

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Associated Press writer Mari Yamaguchi in Tokyo contributed to this report.