The Democratic People's Republic of Korea's ambassador in London was summoned by Asia minister Hugo Swire to the foreign office today, following the reported nuclear test.
North Korea's ambassador, Hyon Hak Bong, was summoned after North Korea reportedly tested a miniaturised hydrogen bomb.
Following the meeting, Swire said that he had summoned the ambassador to express in the "strongest terms the UK's condemnation of their nuclear test".
"This is a clear violation of multiple UN Security Council Resolutions, and the UK supports the resolve of the UN to implement further significant measures against the regime," Swire added. "It is essential, as ever, that the international community is united in its approach and will work on such measures in a new Security Council resolution."
The nuclear test, North Korea's fourth since 2006, came to light after reports of a 5.1 magnitude earthquake near a nuclear testing site in the east Asian country.
"The first H-bomb test was successfully conducted at 10.00am (1.30am GMT) on Wednesday," North Korea's official KCNA news agency said.