SEOUL • North Korea has threatened a further military build-up in response to Mr Joe Biden's condemnation of last week's missile test, which marked Pyongyang's first substantive provocation since the US president took office.

The nuclear-armed North has a long history of using weapons tests to ramp up tensions, in a carefully calibrated process to try to forward its objectives.

Pyongyang had been biding its time since the new administration took office in Washington, not even officially acknowledging its existence until two weeks ago.

But on Thursday it launched two weapons from its east coast into the Sea of Japan, known as the East Sea in Korea.

Mr Biden labelled the test a violation of United Nations resolutions and advised the isolated state against ramping up military testing, warning that "there will be responses if they choose to escalate".

Mr Ri Pyong Chol, a leading official in North Korea's missile programme who supervised the test, said Mr Biden's comments had revealed his "deep-seated hostility" to the regime.

"Such remarks from the US President are an undisguised encroachment on our state's right to self-defence and provocation to it," Mr Ri said in a statement published by state media KCNA yesterday.

He said Pyongyang was expressing its "deep apprehension over the US chief executive faulting the regular test fire, (an) exercise of our state's right to self-defence, as the violation of UN 'resolutions'."

"If the US continues with its thoughtless remarks without thinking of the consequences, it may be faced with something that is not good," Mr Ri added, warning that North Korea was prepared to "continue to increase our most thoroughgoing and overwhelming military power".

The comments come at a time when Washington is in the final stages of a policy review on North Korea, with signals of a firm line on denuclearisation, sanctions and human rights.

North Korea has reported that the Thursday launch, its first substantive affront since Mr Biden came to office, was a test of a new "tactical guided projectile" with a solid-fuel engine.

Japanese Prime Minister Yoshihide Suga called the two weapons launched from North Korea's east coast ballistic missiles, which the isolated country is banned from developing under UN Security Council resolutions.

A UN sanctions committee focused on nuclear-armed North Korea has asked its experts to investigate the test and European members of the Security Council have requested an urgent meeting to discuss North Korea.

AGENCE FRANCE-PRESSE