The South Korean military's joint chiefs of staff announced the launch -- the seventh in two weeks -- without giving further details, Yonhap said.

The Japanese prime minister's office also confirmed the launch on Twitter.

"North Korea has launched a suspected ballistic missile. More updates to follow," the office said.

The missile seems to have fallen outside Japan's exclusive economic zone at sea, the Japanese government said, with the coast guard saying it had so far not received any reports of damage to Japanese ships, national broadcaster NHK reported.

The launch comes after joint military exercises between the United States and South Korea, which Yonhap said concluded Saturday, and joint exercises between the United States, the South and Japan earlier in the week.

Sunday's launch was the latest in a flurry that included an intermediate-range ballistic missile fired Tuesday over Japan, prompting an alert for people in affected areas underneath to take cover.

North Korea on Saturday defended its recent flurry of missile tests as a legitimate counter to US military threats.