Several South Korean cities have canceled exchange programs with Japanese municipalities, amid heightened tensions as Tokyo-Seoul ties tumble to their lowest point in years due to disputes over wartime history and trade policy.

Busan, which is South Korea’s second-biggest city, said Sunday it will suspend administrative exchanges with Japan, including visits by its officials to the neighboring country, until the bilateral relationship improves.

Although the port city has not disclosed all of the programs it will suspend, it cited as an example the signing of an accord with Nagasaki Prefecture on goodwill exchanges. Busan, accessible from the city of Fukuoka by high-speed boats, is known for its active exchanges with Japan.

Busan Mayor Oh Keo-don criticized on July 23 Japan’s tightening of export controls, and indicated that the city would consider whether to continue its exchange programs with Japan.

Chief Cabinet Secretary Yoshihide Suga expressed regret Monday over Busan’s subsequent decision to suspend administrative exchanges with Japan.

“Although ties between Japanese and South Korean governments are in a tough situation, municipal and people-to-people exchanges should continue as the basis of mutual understanding,” said the top Japanese government spokesman.

Earlier this month, Japan imposed tougher export controls on some South Korea-bound chemical materials used to manufacture semiconductors and display panels for smartphones and TVs, triggering fierce opposition from Seoul.

The Asian neighbors are also at loggerheads over South Korean court rulings ordering compensation for wartime forced labor during Japan’s 1910-1945 colonial rule of the Korean Peninsula.

A visit to Ogaki in Gifu Prefecture by some 20 students from Changwon, South Korea, is also postponed “due to the difficult relationship between Japan and South Korea,” according to the Japanese city.

The students were scheduled to play soccer and stay at private lodgings during the four-day trip from Sunday under the exchange program that began in 1996. But an athletic association in Changwon asked its counterpart in Ogaki last Friday to postpone the visit.

Also on Monday, the city of Tenri in Nara Prefecture said Seosan, its sister city in South Korea, had notified Tenri that all exchange programs would be suspended for a while due to worsening Tokyo-Seoul ties. Tenri was supposed to send eight junior high students to Seosan from Tuesday for camping and homestay activities with locals.

According to Tenri, Seosan wrote in an email to the city on Sunday afternoon, “Bilateral ties face a very difficult situation. It is very regrettable but we want to cancel” the hosting of the students.

The two became sister cities in 1991, and have conducted exchanges through mutual visits of students and officials.

“For both Japanese and South Korean people to explore a path to improvement of their ties in a future-oriented manner, grassroots exchanges are all the more important. I am looking forward to the early resumption of exchanges,” said Tenri Mayor Ken Namikawa.

South Korean airlines have also canceled flights to regional Japanese cities, amid a decline in the number of tourists due to the country’s slowing economy as well as the frayed ties with Japan.

According to the transport ministry, 18 local airports across Japan were scheduled to operate 26 regular services to and from South Korea.

However, a Korean Air Lines spokesman said Monday that the firm will suspend its flights between Busan and Sapporo from Sept. 3 because of falling demand as a result of the diplomatic row between the two countries.South Korea’s top carrier is also considering cutting the number of flights between the two countries, or shifting to smaller aircraft from mid-August, he said.

South Korean low-cost carrier T’way Air Co. has decided to cancel five routes linking South Korea with Saga, Kumamoto and Oita by mid-September. The company began suspending flights in late May, starting with the Saga-Daegu route.

A Kumamoto Prefectural Government official quoted T’way as saying that the flights would be canceled as many people are refraining from visiting Japan amid worsening bilateral ties. “I’m concerned about whether this situation will be prolonged or not,” the official said.

Some charter flights operated by Korea Express Air from Gimpo Airport in Seoul to Izumo Airport in Shimane Prefecture have also been suspended, triggering cancellations of hotel and restaurant bookings in the area.

About 20 percent of all foreigners who stayed in Shimane Prefecture last year were from South Korea. “If this situation continues, we will suffer serious damage in the summer holiday season,” said an official of Shimane Prefecture.

In the first half of this year, 3.86 million South Korean people were estimated to have visited Japan — down 3.8 percent from a year earlier in the first decline in five years.

Flights by low-cost carriers to and from regional Japanese cities, which do not carry many business customers, can be affected greatly by changes in demand and subsequent reviews of routes.

“There is nothing we can do,” said an official of the Japanese transport ministry.