North Korea's fifth nuclear test at the Punggye-ri nuclear site had a yield of 10 kilotons.
United Nations, United States:
France urged the UN Security Council on Friday to begin work on a new resolution that would impose fresh sanctions on North Korea after its fifth nuclear test.
"We believe new sanctions are indispensable," French Ambassador Francois Delattre told reporters as he headed into an emergency meeting of the council called to discuss a response to Pyongyang.
"France calls for the adoption as soon as possible of a new resolution under chapter 7" of the UN charter, which provides for sanctions, he added.
The council was meeting at the request of Japan, South Korea and the United States to try to agree on the next steps, but it remained unclear if China, Pyongyang's ally, would support tough measures.
US President Barack Obama earlier vowed to push for new international sanctions in retaliation for the "grave threat" posed by North Korea's latest test.
North Korea's state media said the test, which came after a series of ballistic missile launches, had realized the country's goal of being able to fit a miniaturized warhead on a rocket.
The blast at the Punggye-ri nuclear site had a yield of 10 kilotons, the most powerful to date, according to experts.
The council has strongly condemned North Korea's missile launches and vowed earlier this week to take "further significant measures" against Pyongyang.
Japan and several other council members are calling for new sanctions, but China has repeatedly stressed the need to avoid an escalation of tension on the Korean peninsula.
In a clear reference to China, US Ambassador Samantha Power appealed for council unity, warning that divisions "only embolden the DPRK to further provocations."
North Korea has been hit by five sets of UN sanctions since it first tested a nuclear device in 2006.
The council in March adopted the toughest sanctions resolution to date targeting North Korea's trade in minerals and tightening banking restrictions.
Since that resolution, North Korea has carried out 21 ballistic missile launches, Power said, describing those and Pyongyang's second nuclear test this year as "more than brazen defiance."