SEOUL, South Korea — South Korea’s military says North Korea fired at least one projectile toward its eastern waters, adding to a recent streak in weapons demonstrations.

South Korea’s Joint Chiefs of Staff on Monday did not immediately say whether the weapon was ballistic or how far it flew. The office of Japanese Prime Minister Sanae Takaichi said the country also detected the launch and described the weapon as a suspected ballistic missile.

The launch came days after South Korea on Friday flight-tested its first domestically developed hypersonic weapon, designed to fly at least five times the speed of sound and evade missile defense systems, which President Lee Jae Myung described as an important step in strengthening the South’s conventional defense capabilities.

While maintaining a hard line toward Seoul, North Korea has been ramping up weapons testing as it seeks to expand its arsenal of nuclear-capable systems, including an Oct. 3 test of what the North described as a hypersonic intermediate-range missile designed to evade missile defenses in South Korea and Japan.

North Korea has also conducted other missile tests and live-fire drills and commissioned a new warship as leader Kim Jong Un continues to flaunt his nuclear weapons program while rejecting U.S. and South Korean offers to resume long-stalled diplomacy.

Tensions were further worsened after three South Korean soldiers were injured in land mine explosions last month near the heavily armed inter-Korean border. The South’s military and the U.S.-led United Nations Command concluded the blasts were caused by devices planted by North Korea, which has denied responsibility and ridiculed the South’s demands for an apology.