North Korea missiles launch 'fail over Sea of Japan'

North Korea fired two powerful new mid-range missile on Wednesday which appeared to fail during flight over the Sea of Japan, South Korean military officials said.

The rockets, believed to be an intermediate-range Musudan missile, were launched from the secretive state's east coast, despite being banned by the UN, according to an anonymous official.

A US military spokesman said they had also detected the apparent launch, without providing details.

The second missile is believed to have flown approximately 400 kilometres.

The same day, Japan put its military on alert for a possible North Korean ballistic missile launch, a South Korean news agency reported.

Japanese politicians described the tests as a "grave provocative action", with the country's prime minister warning such ballistic missile launches "clearly cannot be tolerated".

The US stressed the missiles never posed a threat to North America, but a State Department spokesman condemned the launches.

North Korea has failed in all four previous attempts to launch the Musudan, which theoretically has the range to reach any part of Japan and the US territory of Guam.

According to South Korean media, North Korea has up to 30 Musudan missiles.