SEOUL, South Korea — North Korea on Monday test-fired suspected short-range ballistic missiles into the sea, the country’s neighbors said, as speculation swirled that it could soon launch a banned satellite into orbit.

South Korea’s Joint Chiefs of Staff said the weapons launched from the North’s capital region flew about 300 kilometers (185 miles) before crashing in the waters between the Korean Peninsula and Japan. The ranges suggest the weapons could likely target sites in South Korea.

The Joint Chiefs of Staff strongly condemned the launches, saying they were a “clear provocation” that threatens peace on the Korean Peninsula. It said it will maintain readiness to “overwhelmingly” respond to North Korean provocations in step with its military alliance with the United States.

Japan’s Chief Cabinet Secretary Yoshimasa Hayashi told reporters that North Korea launched at least one ballistic missile that flew 250 kilometers (155 miles) at a maximum altitude of about 50 kilometers (30 miles). He said that North Korea's repeated missiles tests and other provocative actions threaten the peace and safety of Japan, the region and the international community.

Japan’s coast guard urged ships to use caution against falling objects, but there were no immediate reports of damage.

North Korea in recent months has maintained an accelerated pace in weapons testing as it continues to expand its military capabilities while diplomacy with the United States and South Korea remained stalled. Observers say North Korea likely believes an upgraded weapons arsenal would give it leverage to win greater concessions from the U.S. if negotiations resume.

North Korea said Saturday that it tested a “super-large” cruise missile warhead and a new anti-aircraft missile in a western coastal area earlier last week. In early April, North Korea also test-launched what it called a solid-fuel intermediate-range missile with hypersonic warhead capabilities, a weapon that experts say is meant to attack remote targets in the U.S. Pacific territory of Guam and beyond.

In past years, North Korea has test-fired nuclear-capable missiles designed to strike sites in South Korea, Japan and the mainland U.S. Many experts say North Korea already possesses nuclear missiles that can reach all of South Korea and Japan, but it has yet to develop functioning intercontinental ballistic missiles that can travel to the continental U.S.

In response to North Korea’s evolving nuclear threats, the United States and South Korea have been strengthening their bilateral military drills and trilateral exercises with Japan. On Monday, the chairman of South Korea’s Joint Chiefs of Staff, Kim Myung-soo, met with U.S. Space Command Commander Stephen N. Waiting for discussions on countering North Korean threats, according to South Korea’s military.

Some experts say North Korea could launch its second spy satellite this month to mark a key anniversary such as the April 15 birthday of its founder Kim Il Sung, the late grandfather of leader Kim Jong Un, or the April 25 founding anniversary of a predecessor of the North’s military.

U.N. Security Council resolutions ban North Korea from launching both ballistic missiles and satellites. The world body considers a satellite launch a test of its prohibited ballistic missile technology.

South Korea’s military said Monday that it had detected evidence that North Korea is preparing for a spy satellite launch but there are no signs that it’s imminent.

Last November, North Korea placed what it called its first military spy satellite into orbit, though there are widespread doubts about its capability. In late December, Kim Jong Un said North Korea would launch three additional military spy satellites in 2024.