N Korea nuke test relatively small-scientists

SYDNEY, Oct 9 (Reuters) North Korea's nuclear test today might have been a ''mini-nuke'' explosion possibly as low as one kiloton, comparable to some small tests by India and Pakistan in 1998, scientists said today.

The US Geological Survey said it had detected a 4.2 magnitude quake in North Korea at 0605 hrs (0135 GMT) today, confirming a similar report from South Korea.

Gary Gibson, senior seismologist at Australia's Seismology Research Centre, said a 4.2 magnitude quake would be the result of a one kiloton explosion.

''It depends on how the thing is set off. There is not a perfect correlation between magnitude and the yield and depends to some extent on the rock type they set it off in,'' he said.

''It is a relatively small nuclear test.'' A US intelligence source agreed that a preliminary examination of the data did not indicate a large blast or a series of explosions.

But the source stressed that analysts were still working towards a definitive evaluation.

''It's premature because they're still evaluating the data,'' the source said.

The RIA news agency quoted today Russian Defence Minister Sergei Ivanov as saying that the nuclear device tested by North Korea ranged between five and 15 kilotons.

The nuclear weapon the United States exploded over Hiroshima in 1945 produced a 12.5-kiloton yield.

Nuclear analyst Andrew Davies, from the Australian Strategic Policy Institute, said if the North Korean test yield was only a kiloton, Pyongyang may be disappointed.

''A kiloton is a very low yield and would tend to suggest, I would have thought, that the device was not all they hoped it would be,'' Davies told Reuters.

''If a nuclear, plutonium bomb fizzles, you can still get one or two kilotons quite easily. You still get a significant energy release. But an efficient device will give you more like 20 (kilotons).'' MINI NUKES The United States has said it is interested in developing so-called ''mini nukes'' -- nuclear weapons with a yield of less of than five kilotons.

A source in Beijing who is close to the North Korean regime said Pyongyang had detonated a neutron bomb, designed to release larger amounts of deadly radiation than other nuclear weapons. There was no immediate confirmation of the claim.

REUTERS PDM PM1640