SEOUL: North Korea fired two short-range ballistic missiles, South Korea’s military said Thursday, shortly after Pyongyang warned of an “inevitable” response to ongoing US-South Korea joint military drills.

South Korea and the United States, which have ramped up defence cooperation in response to growing threats from the nuclear-armed North, are currently carrying out joint large-scale live-fire “annihilation” exercises.

Seoul’s Joint Chiefs of Staff said it had detected the launch of “two short-range ballistic missiles from the Sunan area into the East Sea between 19:25 and 19:37 (1025 to 1037 GMT),” referring to the body of water also known as the Sea of Japan.

“We have stepped up monitoring in case of further provocations and are maintaining readiness in close coordination with the United States,” it said, adding that the launches were a “grave provocation” which violated UN sanctions.

Tokyo also confirmed the missile launches, with a defence ministry official telling reporters that the two missiles had landed in waters within Japan’s exclusive economic zone.

“The missiles may have flown on irregular trajectories,” Japan’s top government spokesman Hirokazu Matsuno told reporters, adding that one had flown 850 kilometres (530 miles) and the other around 900 kilometres at altitudes of 50 kilometres, before landing in Japan’s EEZ.

Relations between the two Koreas are at one of their lowest points in years, with diplomacy stalled and the North’s leader Kim Jong Un declaring his country an “irreversible” nuclear power, as well as calling for ramped-up weapons production, including of tactical nukes.

North Korea has conducted multiple sanctions-busting launches this year, including test-firing its most powerful intercontinental ballistic missiles, and last month attempting to put a military spy satellite into orbit.

In response, the hawkish administration of South Korean President Yoon Suk Yeol has bolstered defence cooperation with the United States and Japan, including expanding joint drills, which had been scaled back because of Covid-19, and during a bout of ill-fated diplomacy.