CHINESE President Xi Jinping has made a plea for cool-headedness over escalating tensions between the US and North Korea.

In a phone conversation with US President Donald Trump yesterday he urged both sides to avoid words or actions that could worsen the situation.

The call came after Trump unleashed a slew of fresh threats against North Korea, declaring the US military "locked and loaded" and warning North Korean leader Kim Jong Un that he "will regret it fast" if he takes any action against US territories or allies.

Trump has pushed China to pressure North Korea to halt a nuclear weapons programme that is nearing the capability of targeting the United States.

China is the North's biggest economic partner and source of aid, but says it alone cannot compel Pyongyang to end its nuclear and missile programmes.

State-run China Central Television quoted Xi as telling Trump the "relevant parties must maintain restraint and avoid words and deeds that would exacerbate the tension on the Korean Peninsula".

But restraint was not the word of the day on Friday as Trump sent out a cascade of unscripted statements, including what appeared to be another red line – the mere utterance of threats – that would trigger a US attack against North Korea and "big, big trouble" for Kim.

North Korea's Minju Joson newspaper hit back at the US in an editorial on Saturday.

"The powerful revolutionary Paektusan army of the DPRK, capable of fighting any war the US wants, is now on the standby to launch fire into its mainland, waiting for an order of final attack," it said.

DPRK is the acronym for North Korea's official name, the Democratic People's Republic of Korea.

The tough talk capped a week in which long-standing tensions between the countries risked abruptly boiling over.

New United Nations sanctions condemning the North's rapidly developing nuclear programme drew fresh ire and threats from Pyongyang.

Trump, responding to a report that US intelligence indicates Pyongyang can now put a nuclear warhead on its long-range missiles, vowed to rain down "fire and fury" if challenged.

The North then came out with a threat to lob four intermediate-range "Hwasong-12" missiles near Guam, a tiny US territory some 3,200 km (2,000 miles) from Pyongyang.

At Trump's New Jersey golf course, the president seemed to put Kim on notice, saying: "If he utters one threat in the form of an overt threat – which by the way he has been uttering for years and his family has been uttering for years – or he does anything with respect to Guam or any place else that's an American territory or an American ally, he will truly regret it and he will regret it fast."

Meanwhile, Japan's prime minister has said he will do everything he can to protect people as tensions escalate over North Korean plans to send missiles flying over Japan toward Guam.

"I will do everything, to the best of my ability, to protect the safety and property of the Japanese people," Shinzo Abe said on Saturday, while visiting his father's tomb in his ancestral home town of Nagato, western Japan.

The Defence Ministry said on Friday it was deploying four surface-to-air Patriot interceptors in western Japan to respond to a possible risk of fragments falling from missiles.

The ministry did not confirm whether defence minister Itsunori Onodera has already issued an order to shoot down incoming missiles.

In another development, Guam residents were warned they should take cover from a North Korean missile attack quickly, in a concrete structure, preferably underground – and stay there until told otherwise, according to a survival guide.

The US island territory's Office of Civil Defence began distributing fact sheets, Preparing for an Imminent Missile Threat, on Friday, to help people prepare for an attack. The guidance includes tips on building an emergency kit, advice on staying put in concrete or brick structures, and reminders about keeping calm.

"Do not look at the flash or fireball – it can blind you", the fact sheet advises those who are caught outside. "Lie flat on the ground and cover your head."

The leaflet also offers guidance on removing radioactive material, saying: "When possible, take a shower with lots of soap and water to help remove radioactive contamination." But do not scratch or scrub skin and "do not use conditioner because it will bind radioactive material to your hair".

Officials have not raised the territory's threat level even after Pyongyang laid out plans to strike near the island in the coming weeks, Guam governor Eddie Calvo said.

He noted that Guam had many buildings made to withstand powerful typhoons, but acknowledged that nothing can protect against a thermonuclear attack.

Trump assured Calvo that Guam was safe, during a phone call. "We are with you a thousand per cent," Trump said, according to video of the call posted on Calvo's Facebook page. "You are safe."

Calvo responded by saying he feels safe and confident with Trump's leadership. "I'm glad you're holding the helm, Sir," he said.

The fact sheets did not seem to cause any widespread anxiety or affect day-to-day Guam life.

Some people wondered about finding plastic sheeting, as one of the leaflets recommends using that and duct tape "to seal all cracks around the door and any vents into the room".