“We are now pressing the Security Council to pass a new resolution as swiftly as possible, imposing further sanctions and showing the unity and determination of the international community,” Johnson told parliament in London.
He said North Korea’s ambassador to Britain had been summoned to the Foreign Office “to receive a formal protest”.
North Korea on Sunday triggered global alarm with by far its most powerful atomic test to date, claiming it was a hydrogen bomb that could be mounted onto a long-range missile.
US Ambassador Nikki Haley told an emergency meeting of the UN Security Council on Monday that Washington will present a new sanctions resolution to be negotiated in the coming days, with a view to voting on it next Monday.
Haley did not spell out what measures Washington was seeking, but diplomats said they could target oil supplies to North Korea — potentially dealing a major blow to the economy.
New sanctions could also seek to curb tourism to the country and ban North Korean labourers sent abroad.
In a phone call with US President Donald Trump on Tuesday, British Prime Minister Theresa May stressed the importance of the UN Security Council quickly agreeing new measures.
“Mrs May said Britain would work with the US and international partners to continue to exert economic pressure on North Korea through further measures including sanctions,” a spokesman for the premier’s office said.
A previous UN resolution adopted in early August banned exports of coal, seafood, iron ore and lead.
In his address, Johnson also called on China to “use all its leverage to ensure peaceful settlement” of the crisis.
“China, which accounts for 90 per cent of North Korea’s overseas trade, has a unique ability to influence the regime,” he said.
China’s ambassador to the UN, Liu Jieyi, urged the parties to agree to a Chinese-Russian plan calling for the North to freeze its missile and nuclear tests and the United States and South Korea to suspend joint military exercises.
