North Korea has threatened unspecified new military measures in response to Japan’s expanding long-range strike capabilities, describing Tokyo’s defence buildup as a direct threat to regional security.

Kim Yo Jong, the influential sister of North Korean leader Kim Jong Un, said Pyongyang would develop “additional military options” as Japan increased its spending, missile capabilities and participation in US-led exercises.

In a statement carried by the state-run Korean Central News Agency on Wednesday, Kim accused Japan of transforming itself into a “war state” and preparing its forces for pre-emptive strikes and operations beyond Japanese territory.

She did not explain what the threatened military options would involve or when North Korea might act.

The immediate trigger for the warning was Japan’s first live launch of a US-made Tomahawk cruise missile. The Aegis destroyer JS Chokai fired the weapon in the Pacific Ocean on 29 July with US Navy support.

Japan’s Ministry of Defence said the exercise confirmed the ship’s new launch capability and its crew’s readiness. The Chokai was modified in the United States and is the first Japanese destroyer equipped to operate Tomahawks.

Kim also cited other Japanese missile tests and the country’s participation in US-led exercises in the Philippines. She accused Washington of enabling Tokyo’s military expansion by supplying weapons, helping modify its ships and supporting its training.

Japan rejects the description of its policy as preparations for a pre-emptive attack. Its defence ministry calls Tomahawks and other long-range weapons “counterstrike capabilities” intended for use after an armed attack.

Defence Minister Shinjiro Koizumi said in March that the weapons constituted the minimum capabilities necessary for self-defence and would not pose a threat to other countries.

Tokyo’s 2026 defence white paper, published on Tuesday, nevertheless calls for Japan to strengthen and transform its armed forces with a greater “sense of urgency and crisis”.

The report describes the country’s security environment as its most severe and complex since the end of the Second World War. It points to China’s military activity, North Korea’s weapons programme and closer cooperation between Pyongyang, Beijing and Moscow.

Japan has been moving away from the strict limits that shaped its post-war defence policy. Its current programme includes long-range missiles, uncrewed systems, stronger coastal defences and wider military cooperation with regional partners.

According to the Stockholm International Peace Research Institute, Japanese military expenditure reached $62.2 billion in 2025, an inflation-adjusted increase of 9.7 per cent from the previous year.

SIPRI calculated that spending at 1.4 per cent of gross domestic product, Japan’s highest military burden since 1958. Tokyo uses a broader measure of defence-related expenditure to say it has reached its target of 2 per cent of GDP.

China has also protested against the new Japanese white paper, accusing Tokyo of exaggerating the threat from Beijing and interfering in the Taiwan issue.

Relations between the two countries deteriorated after Prime Minister Sanae Takaichi said in November that Japan could deploy its Self-Defence Forces if a Chinese attack on Taiwan also threatened Japan’s survival.

Analysts cited by Reuters said Kim’s statement could be intended to provide justification for future North Korean weapons development or military demonstrations. Pyongyang has not announced a test, deployment or other specific response.