North Korea has fired a ballistic missile into the Sea of Japan, South Korea's military has said, ahead of a summit between Donald Trump and his Chinese counterpart in Florida.

The missile was launched from the city of Sinpo – the site of a submarine base - and flew for 40 miles before plunging into the sea.

It comes a day before the start of a meeting between the US President and China's President Xi Jinping in Mar-a-Lago.

The summit is expected to include talks on the nuclear threat from the North.

North Korea attempted to launch a ballistic missile two weeks ago from its east coast and earlier in March fired four missiles towards Japan, some of which came as close as 190 miles from its coast.

Any launch of objects using the ballistic missile technology is a violation of UN Security Council resolutions.

The reclusive state has also conducted two nuclear weapons tests since January 2016.

US defence secretary Jim Mattis condemns 'reckless' North Korea

The US military's Pacific Command said the launch was likely to be of a KN-15 medium-range ballistic missile.

The North is believed to be developing an intercontinental ballistic missile (ICBM) that can hit the United States and its leader, Kim Jong Un, has vowed to test-launch one at any time.

Japan's Chief Cabinet Secretary Yoshihide Suga said the North's missile launch was "extremely problematic" and Tokyo has lodged a strong protest against its nuclear-armed neighbour.

South Korea's presidential Blue House called a National Security Council meeting to review the situation.