The U.S. military has sent a B-52 bomber on a low-level flight over South Korea as a show of force in response to North Korea's latest nuclear test.
The news from North Korea reignited fears in the worldwide community over Pyongyang's efforts to build a warhead small enough to be mounted on a missile and capable of reaching the shores of the mainland US. Speaking at a press conference on Sunday, the head of Japan's Defense Agency Gen Nakatani said the North's recent actions "threaten national security".
Curtis Scaparrotti, head of US military deployment in South Korea, put his troops on the highest alert possible Monday to deter "any provocation coming from North Korea", an official from United States Forces Korea said, according to Reuters.
"B-52 missions reinforce the US commitment to the security of our allies and partners, and demonstrate one of the many alliance capabilities available for the defense of the Republic of Korea", US Seventh Air Force commander, Lieutenant General Terrence O'Shaughnessy, said in an e-mailed statement from USFK.
North Korea is likely to engage in new provocations, Gen. Lee Sun-jin, the chairman of South Korea's Joint Chiefs of Staff, said on a visit to Osan Air Base south of here.
The six-party talks involve South Korea, the DPRK, China, the United States, Japan and Russian Federation.
US leaders discussed Monday sending more strategic American weaponry to its ally South Korea days after North Korea announced it had tested a hydrogen bomb.
As worldwide sanctions punishing Pyongyang for its first three nuclear tests appear to have failed in reining in the North's nuclear program, China is increasingly seen as the only real power with leverage over the Kim Jong-un regime.
The test on Wednesday of what the North claimed was its first hydrogen bomb has sparked global alarm and raised tensions along the inter-Korean frontier, with Seoul reviving cross-border propaganda broadcasts.
North Korea has expanded propaganda broadcasts in border areas in response to South Korea's resumption of such broadcasts, a Seoul official said on Monday.
South Korean measures on the jointly run factory park in the North will take effect on Tuesday.
The broadcasts - which typically include news, weather, anti-North Korea messages and K-pop - are seen as an act of aggression by the North.
South Korea's president Park Geun-hye plans to make a speech to the nation on Wednesday in which she is expected to express strong will to respond to North Korea's nuclear test, a presidential official said.
South Korean conservative activists hold placards showing portraits of North Korean leader Kim Jong-Un during a rally denouncing North Korea's hydrogen bomb test in Seoul on January.