CNN — North Korea may be planning to carry out a new nuclear test, South Korea warned Monday, as the region waits uneasily for Kim Jong Un's next provocative move.
Seoul had already said Sunday that it believed Kim's secretive regime in Pyongyang could conduct a missile test this week after recently moving the necessary components to the coast.
North Korea has issued a catalog of alarming threats against the South and the United States in the past several weeks, sharpening its rhetoric after the U.N. Security Council imposed stricter sanctions for Pyongyang's latest underground nuclear test, which took place it February.
Analysts said at the time that the North might follow up with another detonation soon afterward as it tries to push forward its nuclear program that it says it needs as a deterrent to protect it from the United States.
South Korean Unification Minister Ryoo Kihl-jae told a meeting of lawmakers Monday that North Korea is showing signs it could be preparing to carry out a new nuclear test, the semi-official South Korean news agency Yonhap reported.
Ryoo made the comment in response to a South Korean lawmaker who cited reports suggesting there had been an increase in activity near the site of the North's three previous underground nuclear tests, Yonhap said, adding that Ryoo didn't elaborate further.
A delicate situation
A missile launch and nuclear detonation would put further strain on an already fragile situation on the Korean Peninsula.
The North rattled the region last week by saying it would restart a shuttered nuclear reactor and by preventing South Korean workers and managers from entering a joint industrial zone that is seen as the last major symbol of cooperation between the two Koreas.
Reports then emerged late in the week suggesting the North had loaded as many as two medium-range missiles onto mobile launchers on the east coast ahead of a possible test firing. And the South Korean president's office said Sunday it believed a missile launch could happen around Wednesday.
The North frayed nerves further by warning foreign diplomats inside the country that if war breaks out, it cannot guarantee their safety.
The string of troubling announcements from Pyongyang followed weeks of menacing rhetoric, which included the threat of a nuclear strike on South Korea and the United States.
Observers say they believe North Korea is still years away from having an operational nuclear missile, but they note it does have conventional weapons that pose a threat to countries in the region like South Korea and Japan, both of which are home to thousands of U.S. troops.
Sanctions and drills
The escalation in verbal threats from the North coincided with the tougher U.N. sanctions last month and the annual joint military exercises in South Korea by U.S. and South Korean forces, drills that have aggravated Pyongyang in previous years.
The United States initially responded to the North's invective by publicly drawing to its shows of military force in the training exercises, including the flight of nuclear-capable B-2 stealth bombers over South Korea.
But when those moves appeared to further infuriate rather than intimidate Pyongyang, raising worries that they increased the risk of a miscalculation in the crisis, Washington dialed back the displays of strength.
On Saturday, a senior U.S. Department of Defense official said a long-planned missile test in California, scheduled for Tuesday, was being delayed to avoid any misperceptions by North Korea.
And in a sign of the delicate situation in the region, Gen. James Thurman, the top U.S. commander in South Korea, canceled a trip to Washington this week "as a prudent measure," a U.S. military spokesman said Sunday.
Thurman was due to testify before the Senate Armed Services Committee and the House Armed Services Committee.
In Kaesong, the shared manufacturing zone on North Korea's side of the militarily fortified border with the South, the ban on the entry of new workers and trucks is putting a strain on personnel and supplies, prompting more than 10 companies to cease production.
Analysts have attempted to explain the North's unnerving behavior by suggesting it may be an effort by Kim, who inherited power from his father less than a year and a half ago, to shore up domestic support, particularly with the military.
Another theory is that Pyongyang is trying to secure direct negotiations with Washington, something the United States has long shunned in favor of multilateral talks.
U.S. Secretary of State John Kerry, who will visit Asia this week, is expected to discuss potential diplomatic incentives for North Korea once it stops its threatening rhetoric, senior administration officials told CNN on condition of anonymity.
"Secretary Kerry agrees that we have to have a robust deterrent because we really don't know what these guys will do," said one senior official, who was not authorized to speak on the issue.
"But he also knows that the North Koreans need a diplomatic off-ramp and that they have to be able to see it."
-- CNN's K.J. Kwon, Judy Kwon, Ben Brumfield, Josh Levs, Chris Lawrence, Barbara Starr, Kyung Lah and Jim Clancy contributed to this report.