Korea’s Yonhap news agency quoted unnamed South Korean officials as
saying it was highly likely to have been a nuclear test.
Previous artificial earthquakes in the same area and of that magnitude
have all been nuclear tests.
There has been no comment from the North as yet.
But recent satellite imagery and intelligence has shown indicated
increased activity at the Punggye-ri nuclear site, indicating a fifth
test was imminent.
Friday is also North Korea’s National Day, which celebrates the start of
the country’s leadership regime.
North Korea often uses such events as an opportunity for a show of
Japanese Prime Minister Shinzo Abe said a nuclear test was a
"possibility" and that Japan was closely co-ordinating with its allies.
"If North Korea has conducted a nuclear experiment, we absolutely cannot
condone it. We must protest adamantly."
The US also said it was monitoring the relevant reports.
If this test is confirmed, the biggest question is what might be done,
given that sanctions were tightened after the fourth nuclear test and
North Korea’s launch of a satellite, which its opponents said was really
a test of a missile.
China joined the condemnation but there are fault-lines in its relations
with the US. China doesn’t like the plans to deploy a US anti-missile
defence system in South Korea. It is also angry at condemnation of its
claim to disputed islands.