North Korea solid-fuel rocket
A rocket is launched during a demonstration of a new large-calibre multiple rocket launching system attended by North Korean leader Kim Jong-un (not pictured) at an unknown locationKCNA via Reuters

South Korean President Park Geun-hye has ordered the military to be on high alert after Seoul confirmed North Korea has tested a solid-fuel rocket engine. Park urged the military to brace for more provocation from the other side of the border.

Kim Sung-woo, chief presidential press secretary, told reporters that the South Korean leader "instructed the military to be fully ready to aggressively cope with North Korea's reckless provocations".

Earlier, North Korean leader Kim Jong-un heralded his country's ability to push for the rocket engine, propelled by solid fuel — a significant advance in its nuclear strike capabilities. Though the claims remain to be independently confirmed, Seoul officials have said the North has been pursuing the development of solid fuel for missiles.

"He [Kim] noted with great pleasure that the successful test... helped boost the power of ballistic rockets capable of mercilessly striking hostile forces," said a report by the regime-backed Korean Central News Agency (KCNA).

"This is a historic and unforgettable day," Kim said, as he monitored the tests of solid-fuel missiles. Rodong Sinmun, another state-run mouthpiece, had carried pictures of Kim inspecting a rocket-launching site.

The North's arsenal is known to have liquid-fuelled missiles. But, it had not developed the technology of solid-fuelled medium-range or long-range missiles — which have greater mobility and distinct advantages in military use.

The North has been making a series of claims over its nuclear activities in the past few weeks. This is in addition to issuing threats against the US and South Korea. Pyongyang's latest acts are also in line with zealously developing intercontinental ballistic missiles (ICBM) in a strong show of defiance against UN-led economic sanctions.