SEOUL >> North and South Korea tested ballistic missiles hours apart Wednesday in a display of military might that is sure to exacerbate tensions between the rivals at a time when talks aimed at stripping the North of its nuclear program are stalled.

South Korea’s presidential office said the country conducted its first underwater-launched ballistic missile test. It said the domestically built missile flew from a submarine and hit its designated target.

The statement said the weapon is meant to help South Korea deter external threats — a clear reference to North Korea, which tested two short-range ballistic missile earlier in the day. Those launches came two days after the North said it fired a newly developed cruise missile, its first weapons test in six months.

Experts say the North Korean launches are an effort to apply pressure on the United States in the hopes of winning relief from sanctions aimed at persuading the North to abandon its nuclear arsenal. U.S.-led talks on the issue have been stalled for more than two years — and in the meantime, tensions have been rising on the Korean peninsula.

Meanwhile, observers say South Korean President Moon Jae-in’s government, which has been actively pursuing reconciliation with North Korea, may have taken action to appear tougher in response to criticism that it’s too soft on the North.

The rival nations are still technically in a state of war since the 1950-53 Korean War, which pitted the North and ally China against the South and U.S.-led U.N. forces, ended in an armistice, not a peace treaty.

Japanese Prime Minister Yoshihide Suga said the launches “threaten the peace and safety of Japan and the region and are absolutely outrageous.” The U.S. Indo-Pacific Command said the move “highlights the destabilizing impact of (North Korea’s) illicit weapons program” though it said it didn’t pose an immediate threat to the U.S.

The South Korean test will likely infuriate the North, which has often accused its rival of hypocrisy for introducing modern weapons while calling for talks between the divided countries.

South Korea’s military said the North Korean ballistic missiles flew about 800 kilometers (500 miles) before landing in the waters between the Korean Peninsula and Japan. The launches represent a violation of U.N. Security Council resolutions that bar North Korea from engaging in any ballistic missile activity. But the council typically doesn’t impose new sanctions when the North launches short-range missiles, like Wednesday’s.

Wednesday’s tests came as Chinese Foreign Minister Wang Yi was in Seoul for meetings with Moon and other senior officials to discuss North Korea and other issues.

It’s unusual for North Korea to make provocative launches when China, its last major ally and biggest aid provider, is engaged in a major diplomatic event. But some experts say North Korea may have used the timing to draw extra attention.

Kim Dong-yub, a professor at the University of North Korean Studies in Seoul, said Wednesday’s tests appeared to be of an improved version of a short-range missile it tested in March. He said the weapon is likely modeled on Russia’s Iskander missile, whose flattened-out low altitude flight makes it hard to intercept.

The international community is bent on getting the North to abandon its nuclear program and has long used a combination of the threat of sanctions and the promise of economic help to try to influence the North. But nuclear talks between the United States and North Korea have stalled since 2019, when then-U.S. President Donald Trump’s administration rejected the North’s demand for major sanctions relief in exchange for dismantling an aging nuclear facility.

North Korea leader Kim Jong Un’s government has so far rejected U.S. President Joe Biden administration’s overtures for dialogue, demanding that Washington abandon what it calls “hostile” policies first. But the North has maintained its self-imposed moratorium on nuclear and long-range missile tests, a sign that it may not want to completely scuttle the possibility of reopening the talks.

In 2017, North Korea claimed to have acquired the ability to strike the American mainland with nuclear weapons after conducting three intercontinental ballistic missile tests and its most powerful nuclear test. In recent years, it’s also performed a series of underwater-launched missile tests in what experts say is a worrying development because such weapons are difficult to detect in advance and would provide the North with a second, retaliatory strike capability.

South Korea, which doesn’t have nuclear weapons, is under the protection of the U.S. “nuclear umbrella,” which guarantees a devastating American response in the event of an attack on its ally. But South Korea has been accelerating efforts to build up its conventional arms, including developing more powerful missiles.

Experts say the South’s military advancements are aimed at improving its capacity for preemptive strikes and destroying key North Korean facilities and bunkers.

Separate from the submarine-launched missile, South Korea also tested a missile from an aircraft that is in development.