North Korea has warned of a nuclear attack on the United States, as a US Navy strike group steamed towards the Korean peninsula and US President Donald Trump tweeted that the rogue nation was "looking for trouble".

Key points: North Korea says its "revolutionary strong army is keenly watching" US moves

North Korea says its "revolutionary strong army is keenly watching" US moves Donald Trump has urged China to do more on the North Korea issue

Donald Trump has urged China to do more on the North Korea issue North Korea is set to celebrate the 105th anniversary of Kim Il-sung's birth

Mr Trump, who has urged China to do more to rein in its impoverished neighbour, said in a tweet that the United States would "solve the problem" of North Korea with or without China's help.

Tension has escalated sharply on the Korean peninsula amid concerns that reclusive North Korea may soon conduct a sixth nuclear test and after Washington said at the weekend it was diverting US Navy strike group Carl Vinson from port calls to Australia toward the Korean Peninsula as a show of force.

US officials have stressed that stronger sanctions are the most likely US course to press North Korea to abandon its nuclear program.

But Washington has said all options, including military ones, are on the table and that a US strike last week against Syria should serve as a warning to Pyongyang.

North Korea's official Rodong Sinmun newspaper said the country was prepared to respond to any aggression.

"Our revolutionary strong army is keenly watching every move by enemy elements with our nuclear sight focused on the US invasionary bases not only in South Korea and the Pacific operation theatre but also in the US mainland," it said.

'Everyone should be concerned,' says Pyne

Australia's Defence Industry Minister Christopher Pyne said the North Korean regime was unpredictable and posed the "greatest threat" to global security.

"Everyone should be concerned about the situation on the Korean peninsula," he said.

"We welcome the US taking a firm line with North Korea and as Malcolm Turnbull has said, it is very important that China takes full responsibility for what it can do to settle that part of the world."

Mr Pyne said the unpredictability of the regime was "of significant consequence to Australia".

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 7 minutes 22 seconds 7 m Could Australia be under threat if North Korea goes rogue?

"I know it seems surprising to say so but there is a predictability about the war in the Middle East, in Syria and Iraq, and of course the allies there are winning that war slowly but surely," he told Adelaide radio station 5AA.

South Korea's acting president Hwang Kyo-ahn warned of "greater provocations" by North Korea and ordered the military to intensify monitoring and ensure close communication with Washington.

"It is possible the North may wage greater provocations such as a nuclear test timed with various anniversaries including the Supreme People's Assembly," said Mr Hwang, acting leader since former president Park Geun-hye was removed amid a corruption scandal.

White House spokesman Sean Spicer said Mr Trump had put North Korea "clearly on notice" he would not tolerate certain actions, but dismissed Pyongyang's nuclear attack threat.

"I think there is no evidence that North Korea has that capability at this time," he said.

"Threatening something that you don't have the capability of isn't really a threat."

The aircraft carrier USS Carl Vinson is heading toward the Korean Peninsula. ( Reuters: Tom Tonthat/US Navy, file image )

Trump calls for Chinese action

Mr Trump said in a tweet that a trade deal between China and the United States would be "far better for them if they solved the North Korea problem".

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Mr Trump and his Chinese counterpart Xi Jinping met in Florida last week and the US President pressed Mr Xi to do more to rein in North Korea.

China's ambassador to the United Nations, Liu Jieyi, repeated China's call for a return to dialogue with North Korea.

"The situation is tense and we certainly want a peaceful solution and we believe that it is highly important to move toward denuclearisation, to maintain peace and stability and it's time that different sides sit down to talk about achieving these objectives," he said.

Asked about Mr Trump linking a trade deal to China's help with North Korea: "We need to look at the situation on the Korean Peninsula as something that we should work together on."

North Korea convened a Supreme People's Assembly session on Tuesday, one of its twice-yearly sessions attended by leader Kim Jong-un, and reported a successful national budget execution and personnel appointments, the official KCNA news agency said.

The agency made no mention of North Korea's nuclear weapons program or being under threat from the United States.

North Korea has conducted several ballistic missile tests over the last year. ( KCNA/File Photo via Reuters )

The North has conducted five nuclear tests, two of them last year, and is working to develop nuclear-armed missiles that can reach the United States.

South Korean officials sought to quell talk in social media of an impending security crisis.

"We'd like to ask for precaution so as not to get blinded by exaggerated assessment about the security situation on the Korean Peninsula," Defence Ministry spokesman Moon Sang-kyun said.

North Korea preparing for Kim Il-sung anniversary

Saturday is the 105th anniversary of the birth of Kim Il-sung, North Korea's founding father and grandfather of the current ruler.

A military parade is expected in Pyongyang to mark the day. North Korea often also marks important anniversaries with tests of its nuclear or missile capabilities in breach of UN Security Council resolutions.

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Men and women in colourful outfits were singing and dancing on the streets of Pyongyang, illuminated by better lighting than seen in previous years, apparently practising for the parade.

Syrian President Bashar al-Assad sent congratulations, lambasting "big powers" for their "expansionist" policy.

"The friendly two countries are celebrating this anniversary and, at the same time, conducting a war against big powers' wild ambition to subject all countries to their expansionist and dominationist policy and deprive them of their rights to self-determination," the North's KCNA news agency quoted his message as saying.

Russia's Foreign Ministry said it was concerned about many aspects of US foreign policy, particularly North Korea.

"We are really worried about what Washington has in mind for North Korea after it hinted at the possibility of a unilateral military scenario," the Ministry said.

Reuters