North Korean leader Kim Jong Un inspects a military factory in this undated picture released by the Korean Central News Agency on Friday, May 17. North Korea launched several short-range guided missiles into the sea off the Korean Peninsula's east coast May 18, South Korea's semi-official news agency Yonhap cited the South Korean Defense Ministry as saying.
Kim Jong Un visits the Ministry of People's Security on Wednesday, May 1, as part of the country's May Day celebrations.
A North Korea soldier gestures to stop photographers from taking photos from a Chinese tour boat as other soldiers look on along the North Korean bank of the Yalu River near the town of Sinuiji across the Chinese city of Dandong in Liaoning province, China, on Saturday, April 6.
North Korean soldiers gather by the docks in Sinuiju near the Chinese border on Thursday, April 4.
North Korean soldiers patrol along the Yalu River in Sinuiju across the border from the Chinese city of Dandong on April 4.
Kim Jong Un is briefed by his generals in this undated photo. On the wall is a map titled "Plan for the strategic forces to target mainland U.S."
Kim Jong Un works during a briefing in this undated photo.
North Korean leader Kim Jong Un inspects drills by the Korean People's Army navy at an undisclosed location on North Korea's east coast on March 25 in a photo from the state-run Korean Central News Agency.
Kim makes his way to an observation post with North Korean soldiers on March 25.
Kim uses a pair of binoculars to look south from the Jangjae Islet Defense Detachment near South Korea's Taeyonphyong Island on March 7.
Kim is greeted by the family of a soldier as he inspects Jangjae Islet Defense Detachment near South Korea's Taeyonphyong Island in South Hwanghae province on Thursday, March 7, in a photo from the state-run Korean Central News Agency.
Kim is surrounded by soldiers during a visit to the Mu Islet Hero Defense Detachment near South Korea's Taeyonphyong Island on March 7. North Korea has escalated its bellicose rhetoric, threatening nuclear strikes, just before the U.N. Security Council passed tougher sanctions against the secretive nation on March 7.
Kim arrives at Jangjae Islet by boat to meet with soldiers of the Jangjae Islet Defense Detachment near Taeyonphyong Island in South Hwanghae province on March 7.
Soldiers in the North Korean army train at an undisclosed location on March 6.
North Korean leader Kim Jong Un, center, poses with chiefs of branch social security stations in this undated picture released by North Korea's official news agency on November 27.
Kim celebrates with staff from the satellite control center in Pyongyang, North Korea, during the launch of a rocket carrying a satellite, in a photo released by the official North Korean news agency on December 12.
A crowd watches as statues of the nation's founder, Kim Il Sung, and his son Kim Jong Il are unveiled during a ceremony in Pyongyang on April 13, 2012. Photos from North Korea are rare, but the country was on full display in April 2012 as it celebrated the 100th birthday of Kim Il Sung.
A North Korean soldier stands guard in front of an UNHA III rocket at the Tangachai-ri Space Center on April 8, 2012.
In April 2012, Pyongyang launched a long-range rocket, which broke apart and fell into the sea. The UNHA III rocket is pictured on its launch pad in Tang Chung Ri, North Korea.
A closer look at the UNHA III rocket on its launch pad in Tang Chung Ri, North Korea.
A military vehicle participates in a parade in Pyongyang on April 15, 2012.
North Koreans wave flags in front of portraits of Kim Il Sung, left, and his son Kim Jong Il during celebrations to mark the 100th birth anniversary of Kim Il Sung in Pyongyang on April 16, 2012.
North Korean soldiers relax at the end of an official ceremony attended by leader Kim Jong Un at a stadium in Pyongyang on April 14, 2012.
Kim Jong Un applauds as he watches a military parade in Pyongyang on April 15, 2012.
A North Korean soldier stands on a balcony in Pyongyang on April 16, 2012.
North Korean soldiers march during a military parade in Pyongyang on April 15, 2012.
Soldiers board a bus outside a theater in Pyongyang on April 16, 2012.
North Korean performers sit below a screen showing images of leader Kim Jong Un in Pyongyang on April 16, 2012.
North Korean soldiers salute during a military parade in Pyongyang on April 15, 2012.
Kim Jong Un visits the Rungna People's Pleasure Ground, which is under construction in Pyongyang, in a photo released on July 3, 2012, by North Korea's official Korean Central News Agency.
North Korean soldiers listen to a speech during an official ceremony attended by leader Kim Jong Un at a stadium in Pyongyang on April 14, 2012.
Members of a North Korean military band gather following an official ceremony at the Kim Il Sung stadium in Pyongyang on April 14, 2012.
North Korean military personnel watch a performance in Pyongyang on April 16, 2012.
A North Korean controller is seen along the railway line between Pyongyang and North Pyongan province on April 8, 2012.
A North Korean military honor guard stands at attention at Pyongyang's airport during a diplomatic visit on May 2, 2001.
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
Kim Jong Un and North Korea's military
STORY HIGHLIGHTS
- NEW: U.S. envoy calls North Korean threats "troubling," "counterproductive" and "inflammatory"
- Pyongyang threatens "physical counter-measures" against South Korea
- It says it will act if South Korea takes a "direct part" in new U.N. sanctions
- A day earlier, the North said a new nuclear test would be part of its fight against the U.S.
Seoul, South Korea (CNN) -- "Troubling and counterproductive" rhetoric from North Korea is inflaming tensions on the Korean peninsula, but ultimately, "we will judge North Korea by its actions, not its words," the U.S. envoy to North Korea said Friday.
In its latest bout of saber-rattling, North Korea on Friday warned of the possibility of "strong physical counter-measures" against South Korea after the United Nations imposed tougher sanctions against the North earlier this week.
The threat against South Korea came a day after the North said it would carry out a new nuclear test and more long-range rocket launches as part of a new phase of confrontation with the United States.
The statement Friday from North Korea's Committee for Peaceful Reunification of the Fatherland said it would take action against South Korea if it "takes a direct part" in the U.N. sanctions.
U.N. Security Council slams North Korea
The South Korean Unification Ministry declined to comment specifically on the new threats from Pyongyang. It reiterated its stance that North Korea should refrain from further provocations.
"Now is a moment when I think all parties in the six-party process, in particular here, North Korea, should turn their attention to how to peacefully and diplomatically address challenges that concern them," U.S. envoy Glyn Davies said from Beijing.
North Korea's threats annoy China
North Korea move in 'defiance' of U.N.?
North Korea threatens new nuclear test
Could North Korea strike the U.S.?
The two Koreas have technically still been at war since the all-out conflict between them in the 1950s. Smaller scale clashes have occurred since then, most recently in November 2010 when North Korea shelled a South Korean island, killing several people.
South Korea and the United States are often the focus of menacing language from Pyongyang, but the latest U.N. sanctions, a response to a long-range rocket launched last month by the North, appear to have prompted a ratcheting up of the threats.
Opinion: For the U.N. and North Korea -- Game on
A displeased Chinese editorial
At the same time, North Korea's strong words and vow to conduct a third nuclear test -- previous ones took place in 2006 and 2009 -- appear to be testing the patience of its main ally, China, which voted in favor of the U.N. sanctions this week.
An editorial published Friday in the English-language edition of the state-run Chinese newspaper Global Times struck a displeased tone over Pyongyang's comments a day earlier.
"China's role and position are clear when discussing the North Korea issue in the U.N. Security Council," the editorial said. "If North Korea engages in further nuclear tests, China will not hesitate to reduce its assistance to North Korea."
That prospect carries weight, since North Korea's impoverished economy relies heavily on China to stay afloat.
Global Times, whose editorial line often but not always reflects official Chinese policy, made it clear, though, that Beijing isn't about to cut Pyongyang loose.
Timeline: North Korea's rocket-fueled obsession
"If the U.S., Japan and South Korea promote extreme U.N. sanctions on North Korea, China will resolutely stop them and force them to amend these draft resolutions," the editorial said.
Global Times noted that Beijing had put "a lot of effort into amendments" to the resolution approved by the Security Council this week.
What is a successful rocket launch?
Rocket will provoke 'significant' action
"It seems that North Korea does not appreciate China's efforts," it said. "It criticized China without explicitly naming it in its statement yesterday."
The newspaper was referring to a passage in the controversial North Korean statement Thursday that said that "big countries, which are obliged to take the lead in building a fair world order, are abandoning without hesitation even elementary principle, under the influence of the U.S. arbitrary and high-handed practices."
The Global Times editorial also suggested that North Korea shouldn't rank too highly among China's priorities.
"China hopes for a stable peninsula, but it's not the end of the world if there's trouble there," it said, referring to the Korean peninsula that comprises North and South Korea. "This should be the baseline of China's position."
The Chinese Foreign Ministry on Thursday had urged North Korea and the West to "keep calm, remain cautious and refrain from any action that might escalate the situation in the region."
How dangerous is North Korea's nuke capability?
U.S. concerned but prepared
U.S. Secretary of Defense Leon Panetta said Thursday there are no "outward indications" that North Korea is about to conduct a nuclear test, but he admitted it would be hard to determine that in advance.
"They have the capability, frankly, to conduct these tests in a way that makes it very difficult to determine whether or not they are doing it," he said in a Pentagon press conference.
"We are very concerned with North Korea's continuing provocative behavior," Panetta said, but he added that the United States is "fully prepared" to deal with any provocations.
New nuclear test part of fight against U.S.
CNN's K.J. Kwon reported from Seoul, and Jethro Mullen reported and wrote from Hong Kong. CNN's Jaime A. FlorCruz in Beijing contributed to this report. Mark Morgenstein updated from Atlanta.