Japanese officials said there was no damage to ships or anything else reported. Japan's NHK TV said the missile separated into three parts.

Prime Minister Shinzo Abe told reporters, "We will do our utmost to protect people's lives."

The launch comes days after the North fired what was assessed as three short-range ballistic missiles into the sea and a month after its second flight test of an intercontinental ballistic missile, which analysts say could reach deep into the  US mainland when perfected.

North Korea typically reacts with anger to US-South Korean military drills, which are happening now, often staging weapons tests and releasing threats to Seoul and Washington in its state-controlled media. But animosity is higher than usual following threats by US President Donald Trump to unleash "fire and fury" on the North, and Pyongyang's stated plan to consider firing some of its missiles toward Guam.

Pyongyang regularly argues that the US-South Korean military exercises are an invasion rehearsal. The allies say they are defensive and meant to counter North Korean aggression.

North Korea's UN ambassador, Ja Song Nam, wrote recently that the exercises are "provocative and aggressive" when the Korean peninsula is "like a time bomb."  (AP)