SEOUL, South Korea — North Korea fired two suspected ballistic missiles into the sea Monday in its fourth weapons launch this month, South Korea’s military said, with the apparent goal of demonstrating its military might amid paused diplomacy with the United States and pandemic border closures.

South Korea’s Joint Chiefs of Staff said the North likely fired two short-range ballistic missiles from an area in Sunan, the location of Pyongyang’s international airport. The missiles were launched four minutes apart Monday morning and flew around 380 kilometers (236 miles) on a maximum altitude of 42 kilometers (26 miles) before landing in waters off the country’s northeastern coast, it said.

The U.S. Indo-Pacific Command said the missiles did not pose an immediate threat to U.S. personnel or territory, or to its allies, but highlighted the destabilizing impact of the North’s “illicit” weapons program. Japan’s Defense Minister Nobuo Kishi said the missiles landed outside the Japan’s exclusive economic zone, and the chief cabinet secretary, Hirokazu Matsuno, condemned North Korea’s actions as threats to peace.

South Korean President Moon Jae-in, who is visiting the United Arab Emirates, instructed officials to make “utmost efforts to ensure stability” on the Korean Peninsula, his office said. It also said members of the presidential National Security Council stressed the need to revive nuclear diplomacy with Pyongyang.

North Korea had conducted a pair of flight tests of a purported hypersonic missile on Jan. 5 and Jan. 11 and also test-fired ballistic missiles from a train Friday in an apparent reprisal over fresh sanctions imposed by the Biden administration last week for its continuing test launches.

North Korea has been ramping up tests in recent months of new, potentially nuclear-capable missiles designed to be maneuverable and fly at low altitudes, which potentially improve their chances of evading and defeating missile defenses in the region.

Some experts say North Korean leader Kim Jong Un is going back to a tried-and-true tactic of pressuring his neighbors and the U.S. with missile launches and outrageous threats before offering negotiations meant to extract concessions.

A U.S.-led diplomatic push aimed at convincing North Korea to abandon its nuclear weapons program collapsed in 2019 after the Trump administration rejected the North’s demands for major sanctions relief in exchange for a partial surrender of its nuclear capabilities.

Kim has since pledged to further expand a nuclear arsenal he clearly sees as his strongest guarantee of survival.

His government has so far rejected the Biden administration’s call to resume dialogue without preconditions, saying that Washington must first abandon its “hostile policy,” a term Pyongyang mainly uses to describe sanctions and combined U.S.-South Korea military exercises.

Kim Dong-yub, a professor at Seoul’s University of North Korean Studies, said the North may have conducted another launch to pressure Washington and could continue to dial up its testing activity after vowing stronger action over what it perceives as U.S. hostility.

Last week, the U.S. Treasury Department imposed sanctions on five North Koreans over their roles in obtaining equipment and technology for the North’s missile programs in its response to the North’s earlier tests this month.

The State Department ordered sanctions against another North Korean, a Russian man and a Russian company for their broader support of North Korea’s weapons of mass destruction activities, and the Biden administration also said it would pursue additional U.N. sanctions over the North’s continued tests.

The announcement of the sanctions just came hours after North Korean state media said Kim Jong Un oversaw a successful test of a hypersonic missile on Tuesday, which was the country’s second test of the system in a week, and claimed that the weapon would greatly increase the country’s “war deterrent.”

The North also on Friday fired two short-range ballistic missiles from a train in an apparent retaliation against the fresh U.S. sanctions tied to the hypersonic tests. Friday’s test came hours after the North’s Foreign Ministry issued a statement berating the Biden administration over the new sanctions and warned of “stronger and certain reaction” if Washington maintains its confrontational stance.