SEOUL, South Korea — North Korea said on Thursday that its leader, Kim Jong-un, attended the testing of a new type of large-caliber, multiple-launch, guided rocket system that could expand the North’s ability to strike South Korea and the American forces stationed there.

North Korea said the test-firing of its newly developed rocket system took place on Wednesday, the same day South Korea said the North launched two short-range ballistic missiles that flew 155 miles off its east coast.

It was unclear whether South Korea failed to distinguish large-caliber rockets from ballistic missiles or if the rockets were launched as part of a weapons test that also included ballistic missiles.

In recent years, as the rockets fired by North Korea from multiple-launch tubes flew higher and longer, they have occasionally been mistaken for ballistic missiles.