Opening Monday's meeting, UN Under Secretary General Jeffrey Feltman said North Korea's actions were destabilising global security, and he called on Pyongyang to abide by Security Council resolutions.

"The DPRK [North Korea] is the only country that continues to break the norm against nuclear test explosions," he said.

Ms Haley argued that only the strongest sanctions would enable the problem to be resolved through diplomacy.

North Korean leader Kim Jong-un had shown through his actions that he was "begging for war", she said.

"War is never something the United States wants," she continued. "We don't want it now but our country's patience is not unlimited."

She was speaking after US President Donald Trump warned the US might consider stopping all trade with any country doing business with North Korea.

"The United States will look at every country that does business with North Korea as a country that is giving aid to their reckless and dangerous nuclear intentions," Ms Haley said.

The British ambassador to the UN, Matthew Rycroft, said direct talks with North Korea were only possible if Pyongyang stopped the escalation.

"Dialogue will always be our end goal but returning to dialogue without a serious sign of intent from Pyongyang would be a set-up to failure," he said. "North Korea must change course to allow a return to dialogue."

China's envoy to the UN, Liu Jieyi, reiterated a call for all sides to return to negotiations. "The peninsula issue must be resolved peacefully," he said. "China will never allow chaos and war on the peninsula."

How big was the latest test?

It was North Korea's sixth and most powerful nuclear test to date. The US Geological Survey recorded a resulting tremor at 6.3 magnitude.

Kim Jong-un was shown on camera being shown what state media said was a new type of hydrogen bomb.

South Korea said it was now presumed that the North had reduced its nuclear warhead in size to below 500kg (1,100lbs), and would be able to attach one to an intercontinental ballistic missile (ICBM).

But analysts have said the North's claims about miniaturisation should be treated with considerable caution.

Earlier on Monday, a South Korean defence ministry official said there were signs of "possibly more ballistic missile launches", including an ICBM.

How are the South and its US ally responding?

Monday's drills simulated the targeting of the Punggye-ri nuclear site in Kilju County, where North Korea carried out its bomb test. Missiles were fired from the ground and rockets from fighter jets.

The defence ministry in Seoul said there would be more live-fire drills in the South this month, involving Taurus air-to-surface missiles mounted on F-15 jets.

The ministry also told parliament the US would seek to deploy a nuclear-powered aircraft carrier to seas off the peninsula.

Four more launchers of the US Thaad (Terminal High-Altitude Area Defence) missile defence system -strongly opposed by China and Russia - would also be deployed to join two already at a site in Seongju, south of Seoul.

South Korea and the US have also agreed "in principle" to revise current guidelines so that the South can double the maximum payload of its ballistic missiles, the Yonhap news agency reports.