The United Nations Security Council has condemned North Korea's test-firing of a new ballistic missile and urged its members to "redouble efforts" to enforce sanctions against the reclusive state.

The 15-member council met on Monday after Japan, along with South Korea and the US, asked for an urgent meeting.

Sunday's launch of the Pukguksong-2 missile violated UN resolutions banning ballistic missile launches and marked a major escalation from Pyongyang's shorter-range rocket launches.

It was also the first direct challenge to the international community since US President Donald Trump took office on January 20.

"The members of the Security Council deplore all the Democratic People's Republic of Korea ballistic missile activities, including these launches," it said in a statement.

The council "called upon all member states to redouble their efforts to implement fully the measures imposed on the Democratic People's Republic of Korea by the Security Council".

North Korea has been under UN sanctions since 2006 over its nuclear and ballistic missile tests.

In December, the council adopted a resolution aimed to slash North Korea's exports of coal and other metal exports, designed to cost it $800m a year.

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The US ambassador to the United Nations, Nikki Haley, had tough words for North Korea after the Security Council meeting on Monday.

"It is time to hold North Korea accountable - not with our words, but with our actions," Haley said in a statement.

At a news conference on Monday, Trump said: "Obviously North Korea is a big, big problem and we will deal with that very strongly."

The US "reaffirmed its ironclad security commitments" to South Korea and Japan, the Pentagon said.

Later on Monday, the South Korean defence ministry said the US and South Korea would deploy US strategic assets during their annual joint exercise - in what appeared to be a response to the missile launch.