Reuters: North Korea successfully tested a solid-fuel engine that boosted the power of its ballistic rockets, state media reported on Thursday, as South Korea’s president ordered the military to be ready to respond to the North’s “reckless provocation”.

Pyongyang’s claim indicates it is continuing to develop an intercontinental ballistic missile (ICBM) at a rapid pace in defiance of U.N. sanctions, and amid assessment by the South’s officials that it could conduct a new nuclear test at any time.

The isolated state has in recent weeks stepped up bellicose rhetoric, threatening pre-emptive nuclear strikes against Washington and Seoul, as well as making claims of advancement in its weapons technology.

The Rodong Sinmum, the North’s ruling party newspaper, carried photos of leader Kim Jong Un on site as a rocket engine laid horizontally on the ground emitted a fiery blast. A two-page report detailed the testing of the engine’s structure and thrust.

“He noted with great pleasure that the successful test ... helped boost the power of ballistic rockets capable of mercilessly striking hostile forces,” KCNA news agency said.

The North said last week it had conducted a successful simulated test of atmospheric re-entry of a ballistic missile, and would soon test ballistic missiles capable of carrying nuclear warheads.

On Wednesday, the North repeated the threat to attack the South’s presidential office, saying its large-calibre multiple rocket launch systems are on alert to strike the Blue House and its special operations unit is ready to go into action.