Britain on Tuesday strongly condemned North Korea's announcement that it has staged its most powerful nuclear test yet and called for a "robust response" from the UN Security Council.
"The UK will begin urgent consultations with Security Council partners calling for a robust response to this latest development," British Foreign Secretary William Hague said in a statement.
"North Korea has a choice to make: it can either engage constructively with the international community, cease developing its nuclear and ballistic missile programmes and return to negotiations, or face increasing isolation and further action by the Security Council and the international community."
Hague said the test violated several Security Council resolutions.
"North Korea's development of its nuclear and ballistic missile capabilities poses a threat to international and regional security," he said.
"Its repeated provocations only serve to increase regional tension, and hinder the prospects for lasting peace on the Korean Peninsula."