SEOUL (AFP) - North Korea on Thursday (April 28) tried and appeared to have failed its second attempt in two weeks to launch a powerful, new medium-range ballistic missile, South Korea's Defence Ministry said.

A ministry official said the North had launched what was believed to be a Musudan missile at around 6.40am from Wonsan on the east coast. "It fell within seconds after the launch so (it) is believed to have failed," the official told AFP.

There had been widespread intelligence reports in recent days that the North was preparing for another flight test of its Musudan missile, which is believed to be capable of striking US bases on the Pacific island of Guam.

North Korea initially tried to test a Musudan on April 15 - the birthday of founding leader Kim Il Sung - but the exercise ended in what the Pentagon described as "fiery, catastrophic" failure, with the missile apparently exploding just after take-off.

The failed tests come as the country is gearing up for a rare and much-hyped ruling party congress next month, at which Kim Jong Un is expected to take credit for pushing the country's nuclear weapons programme to new heights.

There is growing concern that Pyongyang is preparing to conduct a fifth nuclear test in the run-up to the event which opens May 6.

Pyongyang has hailed a series of achievements in recent months, including miniaturising a nuclear warhead to fit on a missile, developing a warhead that can withstand atmospheric re-entry and building a solid-fuel missile engine.

Last Saturday, it successfully tested a submarine-launched ballistic missile (SLBM) and was sharply criticised by the UN Security Council.

Existing UN resolutions forbid North Korea from the use of any ballistic missile-related technology.

The Musudan is believed to have an estimated range of anywhere between 2,500km and 4,000km.

The lower range covers the whole of South Korea and Japan, while the upper range would include US military bases on Guam. The missile has never been successfully flight-tested.