Seoul marks Armed Forces Day with flyover of two jets in disputed islands of Dokdo, also known as Takeshima in Japan.

South Korean fighter jets conducted a patrol flight on Tuesday over islands at the centre of a bitter dispute with Japan, South Korean President Moon Jae-in said at an event marking the founding of the South Korean military.

Moon said South Korean F-15K jets patrolled over the disputed islets called Dokdo in Korea and Takeshima in Japan, which are controlled by Seoul and claimed by both countries, a move that could inflame already strained ties between the two.

“Just a moment ago, the F-15K, the most powerful fighter-bomber in Northeast Asia, has returned from completing a patrol mission over our land Dokdo… without any problems,” Moon said in an address to the military.

He made no direction mention of Japan, or North Korea, in his address, but said today’s security climate was highly unpredictable, requiring strength as well as innovation.

“As the recent drone attack in the Middle East region demonstrated to the world, the challenges that we will face will be entirely different from those of the past,” he said.

The South Korean defence ministry clarified two out of the four jets that took part in the patrol flew over the disputed islands.

F-15K jets from the US-based Boeing cost more than $100m a piece in 2006, according to conservative think-tank, The Heritage Foundation.

During the same event, South Korea also showed its newly-acquired F-35 stealth fighter jets from another US-based company, Lockheed Martin.

Seoul currently has eight F-35 jets in its fleet, and it expects 40 of the aircraft to be delivered by 2021. According to a Defense One report in May 2019, the price tag for an F-35 jet sold to the US Air Force is about $80m each.

Worsening diplomatic row

South Korea and Japan have been locked in a worsening diplomatic and trade row rooted in wartime history, and disagreements over compensation for forced labourers during Japan’s 1910-1945 occupation of Korea.

After Japan tightened its curbs on exports of hi-tech materials vital to South Korea’s chip and display industries in July, both countries have removed each other from fast-track trade status.

South Korea will only consider renewing an intelligence-sharing pact with Japan it decided to terminate in August only when Japan’s “unfair export control measures are resolved,” South Korea’s foreign ministry spokesman Kim In-chul told a news briefing on Tuesday.

On Friday, the South Korean government also protested against Tokyo’s annual defence review, which made a reference to Japan owning the islands.

South Korea’s foreign ministry summoned a military official at the Japanese embassy in Seoul to demand an immediate retraction.

In July, a Russian military aircraft twice violated airspace over the disputed islands and drew hundreds of warning shots from South Korean jets, South Korean officials said, during what Russia said was a long-range joint air patrol with China.

Japan, which said it also scrambled fighter aircraft at the time, lodged a complaint with both South Korea and Russia over the incident.

The islands had 28 South Korean residents as of Tuesday, according to South Korean police.

North Korea has criticised the South’s weapons procurements and its joint military drills with the US military as undisguised preparations for war that are forcing it to develop new short-range missiles.

Moon has thrown his support behind dialogue to end the North’s nuclear and ballistic missile programmes, urging that working-level negotiations between the North and the US be held soon. No new dates or locations have been set.