We're pausing our live page coverage for now. You can continue to follow the main developments in our story here. The key points so far are as follows:

• North Korea has tested what it says is a hydrogen bomb that could be loaded on to a long-range missile
• US President Donald Trump said North Korea's "words and actions" were "very hostile and dangerous"
• South Korea, Japan, China and Russia have all voiced strong criticism of the North's sixth nuclear test
• UK Prime Minister Theresa May said the "reckless" test was an "unacceptable further threat to the international community"

Image source, KCNA

US Republican Senator Lindsey Graham told BBC HARDtalk on Saturday that an American first military strike against North Korea is "inevitable" if something does not change.

Mr Graham was speaking to programme host Stephen Sackur at the Ambrosetti Forum in Italy, just hours before North Korea's new claim of a successful hydrogen bomb test.

"I am 100% certain that if Kim Jong-un continues to develop missile technology that can hit America, if diplomacy fails to stop him, there will be an attack by the US against his weapon system. I'm assuming the worst, I'm assuming we drop one bomb, he fires at South Korea and maybe Japan. Let me tell you how the war ends: it ends with his utter destruction. Thousands of people could be killed or maimed.

"There's a lot at stake here. Let me ask you: why would the world allow him [Kim Jong-un] to get a hydrogen bomb with a missile to deliver it anywhere in the world? Why would we do that?"

Japan will work with the US and others to implement existing stringent UN Security Council sanctions resolutions on North Korea, in addition to pursuing the adoption of a new, stricter resolution, says Chief Cabinet Secretary Yoshihide Suga, according to Kyodo News, external.

Mr Suga - the government's top spokesman - said that imposing restrictions on North Korea's trade in crude oil and oil products is "one of the options" Japan might seek.

But he said it would require the agreement of China and Russia, the permanent members of the Security Council with economic ties to Pyongyang.

Chinese President Xi Jinping and his Russian counterpart Vladimir Putin have agreed to stick to their goal of the denuclearisation of the Korean peninsula, according to Chinese news agency Xinhua.

They agreed "to keep close communication and co-ordination to deal with the new situation" and "appropriately deal with" the latest nuclear test, the agency said.

China and Russia have already voiced strong criticism against the latest nuclear test.

Prime Minister Theresa May has spoken about North Korea's test, describing it as "reckless and posing "an unacceptable further threat to the international community".

She added: "I discussed the serious and grave threat these dangerous and illegal actions present with President Abe in Japan this week and reiterate the call we jointly made for tougher action, including increasing the pace of implementation of existing sanctions and looking urgently in the UN Security Council at new measures.

"This is now even more pressing. The international community has universally condemned this test and must come together to continue to increase the pressure on North Korea's leaders to stop their destabilising actions."

Image source, PA

North Koreans gathered in front of a large screen outside Pyongyang Station and applauded as state television broadcast a special announcement confirming the hydrogen bomb test.

Speaking on North Korean TV, Shin Seok Chol said: "I feel great pride in how much our nuclear warheads have advanced in their precision. We can now perfectly rely on our operational ability, and it is astonishing how greatly our nuclear weapons technology has progressed."

Another man, Jang Guk Hwan, said he was "cheering with pride and honour to call myself part of the people of our great and respected leader, Kim Jong-un's nation".

Image source, AFP

"I'm going to draft a sanctions package and send it to the president for his strong consideration so anybody (who) wants to do trade or business with them will be prevented from doing trade or business with us," Treasury Secretary Mnuchin tells Fox News.

"We will work with our allies. We will work with China. But people need to cut off North Korea economically, this is unacceptable behaviour."

US Treasury Secretary Steven Mnuchin is reported to be drafting a new sanctions package on North Korea to give to President Trump. He tells Fox News that will ask the president to "strongly to consider" cutting off all trade and impose new sanctions.

Chinese people felt the ground tremble, but the government is more like to be shaking with anger.

President Trump and his national security team will have a meeting later on Sunday to discuss North Korea's latest nuclear test, a White House statement says.

North Korea is the only country that has performed a nuclear test in the 21st Century, The Washington Post says, external. The paper points out that most nuclear powers - including the US and Russia which between them possess 93% of global nuclear warheads - have not performed a nuclear test in decades.

The apparent hydrogen bomb that North Korea is believed to have detonated underground on Sunday has been estimated at 100 kilotons.

This is five times more powerful than Fat Boy, the bomb dropped on Nagasaki by the US in 1945 and which killed 70,000 people instantly.

But how does it compare with the other big bombs exploded on Earth?

Image source, US Air Force

Regardless of whether it was actually a hydrogen bomb, the explosion was big enough to “pretty much end an American city” if strapped on an ICBM, Vipin Narang, an associate professor of political science at the Massachusetts Institute of Technology tells Bloomberg, external.

Abdul Qadeer Khan, the Pakistani scientist accused of selling nuclear secrets to North Korea, Iran and Libya, has said he is “not surprised” with Pyongyang’s sixth nuclear test, Japanese news agency Kyodo reports.

Mr Khan, who is described as the architect of Pakistan's nuclear weapons programme, has urged Western countries, as well as Japan and South Korea, to stop their "nasty threats and rhetoric" towards Pyongyang.

Image source, AFP/Getty

President Trump's tweet attacking South Korea's "talk of appeasing" North Korea is coming in for some criticism.

Some observers say his stance may be related to a threat to pull the US out of a trade deal with South Korea.

On Saturday reports said Mr Trump had asked aides to prepare for US withdrawal. In July the US told South Korea it wanted to renegotiate a 2012 trade deal, citing a lopsided trading relationship.

In July South Korea proposed holding military talks with the North, after weeks of heightened tension following a long-range missile test by Pyongyang.

Joshua Pollack, associate fellow at defence and security think tank RUSI, said the two were linked.

Meanwhile, others say the US should be showing support for its ally rather than criticising and "threatening a trade war".

And some people - including BBC North America Editor Jon Sopel - are asking how Mr Trump proposes to tackle North Korea.

President Trump has already threatened North Korea with "fire and fury like the world has never seen" - but North Korea has responded by carrying out its biggest-ever nuclear test.

Meanwhile British Foreign Secretary Boris Johnson has condemned North Korea's "reckless" nuclear weapon test and said "all options are on the table".

However he also said there was no easy military solution, as none of the options were good.