[Yonhap Photo]
"Recently, signs of preparations for a fifth nuclear test have been detected," Park told a meeting of aides.
The South's defence ministry also said South Korea has strengthened its watch on the possibility of North Korea carrying out another nuclear test.
Ministry spokesman Moon Sang-gyun told reporters that Pyongyang could conduct a conventional nuclear test or the underground detonation of a warhead without the use of nuclear materials,
"We believe North Korea can conduct a test of both," Moon said, citing an outright order from leader Kim Jong-un last month to carry out a nuclear warhead detonation.
North Korea's nuclear and long-range rocket tests this year triggered tough UN sanctions, but Kim has vowed to step up the development of atomic bombs and rockets capable of carrying nuclear warheads.
Last week, 38 North, the website of a US research institute, reported that North Korea is able to conduct another nuclear test "on short notice", although satellite imagery showed little evidence that there would be a test soon.
Recent satellite imagery showed the presence of a vehicle at the site of the fourth nuclear test in January, as well a few vehicles around it, but there is no apparent activity, it said.
Aju News Lim Chang-won = cwlim34@ajunews.com
reporter
Park Sae-jin
swatchsjp@ajunews.com
