North Korea fired a ballistic missile into waters off its east coast early on Wednesday morning in a new provocation by Pyongyang ahead of talks between US president Donald Trump and Xi Jinping, his Chinese counterpart.

The missile was launched at 6:42am local time near the city of Sinpo and flew around 40 miles before falling into the Sea of Japan, South Korea's Joint Chiefs of Staff announced.

The initial US and South Korean assessments indicated it was a KN-15 medium-range missile, whose first publicly known test in February was described by many foreign experts as a worrying development. It uses solid fuel already loaded inside the missile, which would shorten launch preparation times, boost the weapon's mobility and make it harder for outsiders to detect the signs of its liftoff.

South Korea's foreign ministry called the North's latest missile launch a "reckless provocation" that posed a threat to international peace, while Yoshihide Suga, Japan's chief cabinet secretary, said the country lodged a strong protest over the launch.

A terse announcement from the US department of state stated: "North Korea launched yet another intermediate range ballistic missile. The United States has spoken enough about North Korea. We have no further comment".