North Korea celebrates 'Day of the Sun' with defiant show of might

North Korea responded by warning of a "merciless retaliatory strike" if the US acts first.

Military airplanes flew in formation above Kim Il Sung Square where the day's festivities were held. Coal sales are an important source of revenue for Kim Jong Un's government, and the USA says China has turned back some shipments in recent days.

Among the hardware on display appeared to be new intercontinental and submarine-launched ballistic missiles.

The USS Carl Vinson aircraft carrier has been diverted back to the waters off Korea after heading for Australia, and US satellite imagery suggests the North could conduct another underground nuclear test at any time.

But Choe Ryong Hae, reportedly the second-most powerful official in the country, said in a speech that Pyongyang is prepared for any threat posed by the United States.

"The bottom line is that North Korea has an improving nuclear weapons arsenal", said David Albright, the institute's president.

North Korean school children perform at the Mangyongdae Children's Palace while an image of a space launch vehicle is projected on a screen on Friday in Pyongyang, North Korea.

"As long as dialogue takes place, it can be official or unofficial, through one channel or dual channels, bilateral or multilateral".

The Day of the Sun is the North Korean celebration of the birthday of its founder Kim Il Sung, who died in 1994 but is referred to as the "Eternal President".

North Korea is under United Nations sanctions over its weapons programmes but has long wanted a rocket capable reaching the U.S. mainland.

On display for the first time were what appeared to be the Pukkuksong submarine-launched ballistic missiles (SLBMs), which have a range of more than 1,000 km (600 miles). The country said it could test a nuclear weapon whenever its current leader, Kim Jong Un, decided.

"It is possible the North may wage greater provocations such as a nuclear test timed with various anniversaries".

The official, who wasn't authorized to be quoted by name and demanded anonymity, lamented Pyongyang's "far too common and far too dangerous" provocations, and said Washington would work with worldwide partners to cut the North's government off "from the rest of the world".

"Lately, tensions have risen. and one has the feeling that a conflict could break out at any moment", Chinese foreign minister Wang Yi said, according to AFP. If China decides to help, that would be great. "If not, we will solve the problem without them", he wrote. A carrier strike group led by USS Carl Vinson made its way toward North Korea, in addition to a WC-135 "nuke-sniffer" being deployed to neighboring Japan.

Since taking power in late 2011, Kim Jong Un has executed or purged a slew of high-level government officials in what the South Korean government has described as a "reign of terror". "He's making a big mistake".