The US has deployed F-22 stealth fighter jets to South Korea to join military drills in an attempt to deter further threats from North Korea and underscore America's support for Seoul.
The deployment of the jets on Sunday marks a further escalation of tensions between North Korea and South Korea, backed by the US.
In a statement, the US military command in South Korea said Pyongyang would “achieve nothing by threats or provocations, which will only further isolate North Korea and undermine international efforts to ensure peace and stability in northeast Asia”.
The jets were sent to the Osan Air Base in South Korea from Japan to participate in military exercises which last week involved US B-52 bombers and B-2 stealth bomber being sent to the country. The US military said the drills, called Foal Eagle, underlined America's commitment "of its most advanced capabilities to the security of the Republic of Korea".
US secures west coast
In response to increasingly bellicose rhetoric from North Korea, the Pentagon has also strengthened defences along the US west coast against a potential North Korean missile attack by preparing to add more than a dozen missile interceptors to the 26 already in Alaska.
While warlike rhetoric has dominated proceedings in Pyongyang in recent days, with the annual parliament declaring nuclear weapons and a stronger economy the top priorities, the Supreme People’s Assembly yesterday appointed Pak Pong-ju, seen as an economic reformer, as premier.
The move again raised the issue of possible reform. Mr Pak was sacked in 2007 for introducing an incentive-based wage system, viewed at the time as too capitalistic. His appointment could be a sign Mr Kim is serious about trying to shore up the economy. He has made improving the country's economic plight part of his mission.
The UN estimates two-thirds of the country’s 24 million people face regular food shortages.
The parliament also passed a law “consolidating the country’s status as a defensive nuclear state” and decided to establish a national bureau for space exploration.
Pyongyang is angry about US-South Korean joint military drills and a new round of sanctions by both the UN and the United States following the country's third nuclear test.
Meanwhile, south of the demilitarised zone dividing the two countries, South Korean president Park Geun-hye has instructed the military to strongly respond to possible provocations by North Korea.
South squares up
"Our military exists to defend our nation and its people from such threats," Ms Park told an annual policy plan briefing by the defence ministry.
“If any provocation is made against our people and the country, [the military] should strongly respond in an early stage without any other political considerations.”
Ms Park is keen to present a robust counter-threat to North Korean sabre-rattling given the widespread criticism in South Korea of the government’s weak reaction to the sinking of a South Korean warship and the shelling of an island in 2010, which killed 50 South Koreans.
Pyongyang’s on-off negotiations saw it take part in nuclear disarmament talks for five years aimed at paying it off to abandon its atomic programme.
Those talks fell apart in 2008. Some experts say the talks gave the North grounds to pursue a highly enriched uranium programme that took it closer to owning a working arsenal.
White House National Security Council spokeswoman Caitlin Hayden said North Korea’s announcement that it was in a state of war followed a “familiar pattern” of rhetoric.
China has repeatedly called for restraint on the peninsula. However, many in South Korea regard the North’s willingness to keep open the Kaesong industrial zone, a few miles north of the border and operated jointly by both sides, as a sign Pyongyang will not risk losing a lucrative source of foreign currency.
