David Cameron underlined the need for the UK to maintain its nuclear deterrent after claiming that North Korea could launch a missile attack on Britain.
The Prime Minister said the actions of Kim Jong-un's regime were "worrying and threatening" and the country had "extremely dangerous" weapons.
Speaking at a PM Direct event in Glasgow, he added that the threat posed by North Korea was a "real concern."
ITV News International Editor Bill Neely reports:
– David Cameron
North Korea does now have missile technology that is able to reach, as they put it, the whole of the United States.
So if they are able to reach the whole of the United States, they can reach Europe too.
They can reach us too. So that is a real concern.
Mr Cameron added that maintaining the UK's nuclear capacity was a necessary "insurance policy against the risks that there are in the world".
Tensions on the Korean peninsula have increased in recent weeks due to a string of a provocative comments from Pyongyang.
North Korea's military warned the US it had received final approval to launch "merciless" strikes using "smaller, lighter and diversified" nuclear weapons.
A missile with "considerable range" has reportedly been moved to the country's east coast.
The US announced that it will deploy a THAAD missile defence system to the US Pacific territory of Guam to strengthen regional protection against a possible attack.
Russia said Pyongyang's threats meant that any chance of resuming the "six-party talks" were now "radically" complicated.
Russian foreign ministry spokesman Alexander Lukashevich added that North Korea's attempts to "violate decisions of the UN Security Council are categorically unacceptable."
North Korea's state-run TV channel KRT broadcast what it claimed was footage from anti-US rallies held across the country.
ITV News cannot independently verify the content of this video.
Meanwhile, the heightened tension in the Korean peninsula could affect the disputed island of Yeonpyeong.
Two and a half years ago, the last time the conflict escalated, the North Koreans fired almost 200 artillery shells and missiles at the island.
Damage was extensive and the South Koreans preserved bombed out houses to remind them of their enemy.