North Korea fired what appeared to have been an intermediate range ballistic missile on Thursday but it crashed seconds after the test launch, South Korea's defence ministry said, the second such failure in the run-up to next week's ruling party congress.

Isolated North Korea has conducted a flurry of missile launches, in violation of UN resolutions, and tests of military technology ahead of the Workers' Party congress that begins on May 6, and Thursday's launch looks to have been hurried, according to a defence expert in Seoul.

A South Korean defence ministry official told Reuters that the launch at about 6:40 a.m. local time (2140 GMT Wednesday) from near the east coast city of Wonsan appeared to have been of a Musudan missile with a range of more than 3,000 km (1,800 miles).

It crashed within seconds, the official said.

‘They are in a rush to show anything that is successful, to meet the schedule of a political event, the party congress,’ said Yang Uk, a senior research fellow at the Korea Defence and Security Forum and a policy adviser to the South Korean navy.

‘They need to succeed but they keep failing. They didn't have enough time to fix or technically modify the system, but just shot them because they were in hurry,’ he said.

Thursday's apparent failure marks another setback for the North's young leader Kim Jong Un. A similar missile launched on the April 15 birthday of his grandfather, the country's founder, Kim Il Sung, exploded in what the US Defense Department called a ‘fiery, catastrophic’ failure.

Some experts had predicted that North Korea would wait until it had figured out what went wrong in the previous failed Musudan missile launch before attempting another, a process that could take months and a sign that Thursday's firing was rushed.

However, South Korea's Yonhap news agency had reported on Tuesday that the North appeared to be preparing the second launch of a Musudan, which theoretically has the range to reach any part of Japan and the US territory of Guam. According to South Korea, the missile has never been successfully flight-tested.

North Korea lists South Korea, the United States and Japan as its main enemies.

South Korea also says the North is ready to conduct a  nuclear test at any time. It would be its fifth nuclear test.

‘Signs for an imminent fifth nuclear test are being detected ahead of North Korea's seventh Party Congress,’ President Park Geun-hye said at a national security meeting on Thursday.

DID NOT FLY HIGH

The defence ministry official, who declined to be identified by name, said South Korean and US officials were analyzing the cause of Thursday's missile crash, declining to comment on why news of the launch was revealed several hours after it took place.

Yonhap said the fired missile was not detected by South Korean military radar because it did not fly above a few hundred metres, and was spotted by a US satellite.

The South Korean defence ministry told Reuters it could not confirm that report.

North Korea's missile tests are in defiance of United Nations Security Council sanctions against the country, which were strengthened following a January nuclear test and a space rocket launch the following month.

On Saturday, North Korea tested a submarine-launched ballistic missile, which travelled about 30 km (18 miles) off its east coast.