North Korea has fired several short-range missiles from its east coast, South Korea's military has said.

It is the first missile launch since 2017 as the country steps up pressure against Washington after a failed nuclear summit in February.

The North fired an unidentified short-range missile from the city of Wonsan around 9am local time, South Korea's Office of the Joint Chiefs of Staff said in a statement.

The Office said it was conducting joint analysis with the United States.

Several missiles flew 70km to 200km, the Joint Chiefs of Staff said later.

The launch is the first since the North fired an intercontinental ballistic missile (ICBM) in November 2017, before declaring the building of its nuclear force complete and extending an olive branch to the South and the United States.

The country’s leader, Kim Jong-un, has vowed to no longer test nuclear weapons or ICBMs, but the North has conducted other weapons tests since then.

The missile firing, coming after the North's test of what it called a tactical weapons system, added to the pressure it has exerted on Washington in talks on ending the North's nuclear programme.

"It also seems clear that North Korea is angry over what appears to be a lack of flexibility in the Trump administration’s position on relieving sanctions, sticking to a policy of 'maximum pressure'," said Harry Kazianis at the Centre for the National Interest, a think-tank.

Mr Kim has held two summit meetings with US President Donald Trump, the second in February in Vietnam, but the two failed to make progress on ending the North's nuclear programme due to disagreement on weapons dismantlement and sanctions relief.