North Korea appears to be preparing for a fourth nuclear test, according to South Korean officials.
South Korean Unification Minister Ryoo Kihl-jae told lawmakers there were signs of increased activity in North Korea’s main nuclear test site.
North Korea has stepped up its habitual fiery rhetoric against the US and South Korea in recent weeks.
Correspondents say it is unclear whether a test is being prepared or it is a ruse to boost the sense of crisis.
Ryoo Kihl-jae did not elaborate on the specific intelligence which led South Korea to suspect the North was set to carry out its fourth nuclear test.
But when asked about a news report that North Korea had stepped up activity at the underground site it has used in previous tests, he said “there are such signs”.
Kim Min-seok, a spokesman for South Korea’s defense ministry, said it was possible that the North could fire a ballistic missile and conduct a nuclear test at the same time.
But South Korean official Yonhap news agency quoted him as playing down the threat of an imminent test, saying there were several facilities at the nuclear test site so the movement of vehicles and people there was expected.
“Currently, there is no new movement to add on to the previous briefing,” he said.
Newspaper JoongAng Ilbo quoted an unnamed South Korean official as saying that South Korean intelligence had detected “increased activity of labor forces and vehicles” at the Punggye-ri nuclear test site in the country’s north-east.
“We are closely monitoring the ongoing situation, which is very similar to the situation ahead of the third nuclear test,” the official told the newspaper.
“We are trying to figure out whether it is a genuine preparation for a nuclear test or just a ploy to heap more pressure on us and the US.”
The UN imposed tough sanctions on North Korea last month following its third nuclear test. Pyongyang responded by stepping up angry rhetoric, including threats to use nuclear weapons and restarting its nuclear reactor.
In recent weeks, North Korea has shut down an emergency military hotline between Seoul and Pyongyang, stopped South Koreans from working at the Kaesong joint industrial complex and warned it would not be able to guarantee the safety of foreign embassy staff in the event of a war.
On Monday, the North Korea’s state news agency said a senior official had visited the Kaesong complex and told workers there to prepare for all possible developments.
Analysts have suggested that the rhetoric is in large part designed to shore up the standing of a young, inexperienced leader, Kim Jong-un, in the eyes of his own people.
North Korea’s state media have been broadcasting a continuing diet of war and retribution with programmes about biochemical war, nuclear war and military preparations dominating the listing.
Meanwhile, Japan’s defense ministry said the country’s armed forces have been ordered to shoot down any North Korean missile headed towards its territory.
Over the weekend, the US cancelled a scheduled test of its Minuteman III ballistic missile, citing concerns that it could be misinterpreted by Pyongyang.