Scientists around the world are taking a cautious wait-and-see attitude after North Korea claimed to have successfully conducted an underground nuclear test on Monday.

Only careful analysis of data returned by seismic or atmospheric sensors will determine whether the blast was a success or a damp squib, they say. Nor could they rule out the possibility of a scam, in which North Korea blew up a huge stock of conventional explosives to bolster its claim to have joined the nuclear club.