The US and South Korean militaries launched eight ballistic missiles into the sea on Monday in a show of force matching a North Korean display a day earlier.

South Korea’s Joint Chiefs of Staff said the allies’ live-fire exercise involved eight Army Tactical Missile System missiles fired into South Korea’s eastern waters across 10 minutes. It said the drill was aimed at demonstrating an ability to respond swiftly and accurately to North Korean attacks.

The South’s military on Sunday detected North Korea firing eight short-range missiles over 35 minutes from at least four different locations, including from western and eastern coastal areas and two inland areas north of and near the capital, Pyongyang, in what appeared to be a single-day record for the country’s ballistic launches.

It was North Korea’s 18th round of missile tests in 2022 alone — a streak that included the country’s first launches of intercontinental ballistic missiles (ICBM) in nearly five years.

South Korean and US officials also say North Korea is preparing to conduct its first nuclear test since September 2017 as leader Kim Jong Un pushes brinkmanship aimed at cementing the North’s status as a nuclear power and negotiating economic and security concessions from a position of strength.

US and South Korean forces conducted a similar live-fire drill following North Korea’s previous ballistic launches on May 25, which South Korea’s military said involved an ICBM flown on medium-range trajectory and two short-range weapons. Those tests came as President Joe Biden wrapped up his trip to South Korea and Japan, where he reaffirmed the US commitment to defend both allies.

North Korean state media have yet to comment on Sunday’s launches. They came after the US aircraft carrier Ronald Reagan concluded a three-day naval drill with South Korea in the Philippine Sea on Saturday, apparently their first joint drill involving a carrier since November 2017, as the countries move to upgrade their defence exercises in the face of North Korean threats.

North Korea has long condemned the allies’ combined military exercises as invasion rehearsals and often countered with its own missile drills, including short-range launches in 2016 and 2017 that simulated nuclear attacks on South Korean ports and US military facilities in Japan.

Hours after the North Korean launches, Japan and the United States conducted a joint ballistic missile exercise aimed at showing their “rapid response capability” and “strong determination” to counter threats, Japan’s Defence Ministry said.

The US has vowed to push for additional international sanctions if North Korea conducts a nuclear test, but the prospects for meaningful new punitive measures are dim with the UN Security Council’s permanent members divided.

Russia and China vetoed a US-sponsored resolution that would have imposed additional sanctions on North Korea over its latest ballistic tests on May 25, insisting that Washington should instead focus on reviving negotiations with Pyongyang.

Those talks have stalled since 2019 over disagreements in exchanging the release of crippling US-led sanctions for the North’s disarmament steps.

Despite facing harsh challenges at home, including a decaying economy and a Covid-19 outbreak, Mr Kim has shown no willingness to fully surrender an arsenal he sees as his strongest guarantee of survival.

His government has so far rejected the Biden administration’s offers for open-ended talks and is clearly intent on converting the dormant denuclearisation negotiations into a mutual arms-reduction process, experts say.