The UN Security Council yesterday agreed to roll out new measures to punish North Korea after Pyongyang announced it had carried out a successful hydrogen bomb test -- a claim rejected by Washington.

With backing from China, Pyongyang's main ally, the 15-member council strongly condemned the test and said it would begin work on a new UN draft resolution that would contain "further significant measures."

UN diplomats confirmed that talks were underway on strengthening several sets of sanctions that have been imposed on North Korea since its first tested an atomic device in 2006.

Pyongyang's announcement drew swift condemnation from the international community, including from China and Washington, which said an initial analysis was "not consistent" with North Korea's claims of a successful hydrogen bomb test.

South Korean President Park Geun-Hye condemned what she described as a "grave provocation" and called for a strong international response.

"I demand the DPRK cease any further nuclear activities," UN Secretary General Ban Ki-moon said.

Skeptical experts suggested the apparent yield was far too low for a thermonuclear device.

North Korean state television announced "the republic's first hydrogen bomb test," which was "successfully performed at 10:00am (0130 GMT)."

"We have now joined the rank of advanced nuclear states," it said, adding that the test was of a miniaturized device.

State television showed North Korean leader Kim Jong-Un's signed order -- dated December 15 -- to go ahead with the test and begin 2016 with the "thrilling sound of the first hydrogen bomb explosion."

The UN Security Council met behind closed doors at the request of the United States and Japan, who led the push for fresh punitive measures.

"We will be working with others on a resolution on further sanctions," British Ambassador Matthew Rycroft told reporters.

In a unanimous statement, the council said it "strongly condemned" the underground test and described it as a "clear threat to international peace and security."