South Korean and USA officials have feared for some time that a sixth North Korean nuclear test could be imminent.
Nonetheless, it appears that the us hasn't ruled anything out yet.
Princeton University professor Aaron Friedberg said North Korea could begin with a massive artillery barrage against Seoul, and unleash special forces and chemical and biological weapons, even if that would lead to the annihilation of Kim Jong Un's North Korean dictatorship.
It highlights Chinese fears that tensions between the United States and North Korea could erupt into conflict.
Kim reported from Seoul, South Korea.
South Korea's Yonhap news agency, citing an unnamed government source, reported that Pyongyang appeared to have deployed a number of long-range artillery units in the region of Wonsan, which is a coastal North Korean area.
PYONGYANG, North Korea (AP) - South Korea's military said Tuesday that North Korea held major live-fire drills in an area around its eastern coastal town of Wonsan as it marked the anniversary of the founding of its military.
Chinese President Xi Jinping urged "restraint" on North Korea during a phone call on Monday with US President Donald Trump, days before an American supercarrier is due to arrive in the Korean Peninsula. He praised China for its recent steps seen more cooperative toward that goal.
"The other speculation is whether or not China will actually listen to the United States and want to pressure the North in stopping its development regarding nuclear weapons technologies and others because for the Chinese it is also important for the North Korean regime to remain intact", commented Ko.
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In a statement, the military said it had dispatched a transport helicopter to move those in need of critical medical care. The violence sparked protests by local residents in Parachinar, the administrative headquarters of the agency.
Mr Trump later told UN Security Council ambassadors "the status quo" was not acceptable and said the council must be ready to impose new sanctions.
North Korea's leader Kim Jong Un did not attend.
Trump sent the USS Carl Vinson aircraft carrier strike group for exercises off the Korean peninsula as a warning to Pyongyang, but US officials say sanctions, not military strikes, are the preferred option.
A White House readout of the call said Trump criticized North Korea's "continued belligerence" and the leaders "reaffirmed the urgency of the threat".
Japan's Foreign Ministry also announced that China's envoy for North Korea, Wu Dawei, is arriving in Tokyo on Tuesday for talks with Kanasugi, which may take place later this week.
US envoy for North Korea Joseph Yun says he and his counterparts from Japan and South Korea agreed to coordinate "all actions" on North Korea.
At the Senate Armed Services Committee hearing Tuesday, U.S. lawmakers probed experts on the potential consequences of a pre-emptive U.S. military strike on North Korea.
Tillerson, along with Defense Secretary Jim Mattis, Director of National Intelligence Dan Coats and Joint Chiefs chairman General Joseph Dunford, would also hold a rare briefing for the entire U.S. Senate on North Korea on Wednesday, Senate aides said. On Friday, Tillerson will host a meeting on North Korea at the UN.
Seoul has long anxious about losing its voice in global efforts to deal with North Korea's nuclear threat - something local media have termed "Korea Passing". That statement did not directly follow with what was publicly stated by U.S. officials or by U.S. Pacific Command, which released a press statement noting the cancellation of a port visit for the Vinson in Australia.