North Korea fired four ballistic missiles early Monday morning in what Japan's leader described as "an extremely dangerous action."

A fifth missile failed to launch, a US official told CNN.

Military authorities in South Korea, Japan and the United States all confirmed the launch of four projectiles, which traveled almost 1,000 kilometers (620 miles) towards the Sea of Japan, also known as the East Sea. One US official said they were intermediate-range missiles.

Three landed inside Japan's exclusive economic zone, Prime Minister Shinzo Abe said, which extends 200 nautical miles from its coastline, according to international maritime law.

The launch underscored the rapid evolution of North Korea's weapons program, which experts say has begun moving at a faster rate to develop and deploy missiles.