North Korea fired multiple unidentified cruise missiles on Sunday in a move that comes as leader Kim Jong Un ramps up his rhetoric about a potential conflict with the U.S. and South Korea.

Multiple projectiles were detected around the waters near the North Korean port city of Shinpo, South Korea’s Joint Chiefs of Staff said in a text message. South Korea’s military “strengthened its guard and is closely cooperating with the U.S.,” it added.

North Korea fired off an intermediate-range ballistic in early January designed to hit U.S. bases in Asia for its first such launch of 2024. The state’s official media said it was a “hypersonic” missile, indicating it deployed a reentry vehicle that could hold a nuclear warhead and maneuver at high speeds.

North Korea followed that by firing multiple cruise missiles into waters off its west coast and tearing down a monument dedicated to reunification with South Korea as leader Kim intensified a pressure campaign against his neighbor.

Kim appears to be transferring massive amounts of weapons to Russia for President Vladimir Putin to use in his war on Ukraine. The arms include artillery shells and ballistic missiles, the U.S. and South Korea has said. Russia is likely providing technology, key materials and commodities to Kim that could help him expand the economy and increase his military strength, which firms his grip on power.

While the assistance may allow Kim to shun engagement with the West for years to come, it also reduces pressure on the 40-year-old leader to gamble on more drastic measures, including war.

North Korea and Russia have denied accusations of arms transfers but satellite imagery since October shows a steady flow of shipping between the two neighbors likely conducted in territorial waters of the two to avoid international interdiction.

Pyongyang fired 30 ballistic missiles and three space rockets in 2023. They included five intercontinental ballistic missiles that could hit the U.S. mainland. Kim’s regime launched more than 70 ballistic missiles last year, a record for the state.

Kim has ignored U.S. calls to return to long-stalled nuclear disarmament talks through which Pyongyang could secure economic aid in exchange for disarmament. But he has been busy modernizing his arsenal of missiles and conducting tests of systems to attack South Korea and Japan, which host the bulk of U.S. military personnel in the region.

North Korea in late September enshrined its policy of exponentially growing its nuclear forces into its constitution, with Kim saying he was making the move to counter threats from the U.S. and its partners to stifle Pyongyang’s atomic ambitions and destroy its system.