Tokyo on Sunday protested South Korean military exercises that Seoul said were intended to “defend” a cluster of rocky islands that both nations claim, calling the drills “unacceptable,” just days after the South said it would leave a key intelligence-sharing pact it had signed with its Asian neighbor.

The South Korean Defense Ministry said in a statement that the two days of drills involve naval vessels, aircraft, as well as army and marine corps units on and around the islets, which Tokyo calls Takeshima and Seoul calls Dokdo.

The war games were likely to further inflame already fraught ties between the countries after South Korea bolted from the General Security of Military Information Agreement (GSOMIA) over a trade and history row with Japan.

Japan’s Foreign Ministry issued a strong protest with the South Korean side, with Kenji Kanasugi, director-general of its Asian and Oceanian Affairs Bureau, telephoning a minister at the South Korean Embassy in Tokyo to protest.

“It is clear Takeshima is part of Japanese territory in light of historic facts and international law,” Kanasugi told the minister. “The drills are totally unacceptable and very regrettable.”

The South’s presidential Blue House said the drills are intended to show Seoul’s resolve to defend the islands and the area surrounding the East Sea, which Tokyo calls the Sea of Japan.

“Indeed, it’s an exercise to guard our sovereignty and territory,” the Yonhap news agency quoted Blue House spokesperson Ko Min-jung as saying at a news conference.

Ko called the exercises regular training and asked media not to attach excessive “political” meaning to them.

She said the training is aimed at improving the military capability against potential threats from “all forces,” not just Japan.

The military initially planned to hold this year’s first drills in June, but put them off amid increasing concerns about souring bilateral ties.

Asked about the schedule of this year’s exercise, Ko said that weather conditions and “various other” factors were considered.

The islets, which Japan claims as part of Shimane Prefecture but have been controlled by Seoul since Tokyo’s colonial rule of the Korean Peninsula ended in 1945, are home to a small South Korean military detachment. The South first staged the twice-yearly drills in 1986 and usually conducts them in June and December.

The military also expanded the size and scale of this year’s drills to cover a wider area in the waters around the islets, which sit between the two countries, according to South Korean media reports.

According to the South Korean Navy, the country’s first Aegis-equipped destroyer, Sejong the Great, and nine other warships and 10 warplanes have been deployed in the drills.

“Overall, the size of the armed forces doubled compared with previous levels,” Yonhap quoted a navy official as saying.

Ties between Seoul and Tokyo have sunk to new lows in recent weeks, after Japan dropped South Korea from a list of trusted trading partners earlier this month following the announcement of tighter export curbs on July 4. In response, South Korea on Thursday announced its decision to terminate the military information-sharing pact with Japan.

Trust between the two countries’ militaries has also eroded significantly since an incident last December in which a South Korean warship allegedly directed its fire-control radar at a Maritime Self-Defense Force patrol plane.

In July this year, Chinese and Russian military planes flew over the Sea of Japan in what the two countries claimed were joint patrols. When one of the Russian planes violated airspace over the disputed islets during the operations, South Korean fighter jets fired hundreds of warning shots.

Observers say the expanded area of the drills may have reflected these developments.