A small earthquake that occurred early on Saturday near North Korea's known nuclear test site was likely a natural quake, South Korea's weather agency said, amid heightened concern about a possible nuclear test by Pyongyang.
A 2.5-magnitude quake shook an area just northeast of North Korea's Punggye-ri nuclear test site at 2:54 a.m. local time (1754 GMT, Friday), the Korea Meteorological Administration of South Korea said.
"It is assessed to be a natural earthquake," the agency said in an advisory. It gave the depth of the tremor at 23 kilometres (14.3 miles).
The area is the location of small quakes earlier in the year which analysts said were because of geological instability stemming from activities at the test site.
North Korea is believed to have completed preparations for a seventh nuclear test at the Punggye-ri test site, which would be the first since 2017, officials in Seoul and Washington have said.
A possible window for carrying it out could be between Oct. 16 and Nov. 7, South Korean lawmakers said last week, citing the country's intelligence agency which briefed them. But Defence Minister Lee Jong-sup said it was hard to predict when the North would conduct a new test.
South Korea and the United States are holding joint naval exercises involving a U.S. aircraft carrier this week after North Korea fired a series of ballistic missiles including a intermediate range ballistic missile over Japan on Tuesday.
(Reporting by Jack Kim; Editing by Leslie Adler)
