New analysis of North Koreas Sept. 3 nuclear test the regimes sixth-ever and most powerful to date suggests it could have been twice as strong as previously thought.

Initial estimates had put the blasts yield at about 120 kilotons, but updated seismic data reveals it was likely around 250 kilotons approximately 17 times as powerful as the bomb used to decimate the Japanese city of Hiroshima during World War II.

A new report from 38 North , a website run by the US-Korea Institute at Johns Hopkins University, explains that revised seismic estimates raise the blasts magnitude from 5.8 to 6.1, which in turn raises its estimated yield to one-quarter megaton of energy. This figure approaches what 38 North had concluded to be the maximum yield that North Koreas underground Punggye-ri nuclear test site could contain.

In their preliminary assessments, the Japanese, U.S. and South Korean governments said the yield was 160, 140 and 50 kilotons , respectively.

Pyongyang claims it detonated a hydrogen bomb in this latest test, which its state media swiftly described as a perfect success.

On Wednesday, South Korea confirmed reports that it had detected radioactive gas from the nuclear site, but remained unable to verify whether a hydrogen bomb had in fact been used.

The international community has scaled up efforts to rein in North Korea, which has long been hell-bent on nuclear advancement , in light of its nuclear test earlier this month and its string of recent missile launches.

The United Nations Security Council approved fresh sanctions against Pyongyang in a unanimous vote on Monday, slashing the cap on crude and refined oil exports to the country by 30 percent. The sanctions also ban textile imports from North Korea a vital industry in the Hermit Kingdom.

North Korea responded to the vicious sanctions by vowing to inflict the greatest pain the U.S. has ever suffered.

My delegation condemns in the strongest terms and categorically rejects the latest illegal and unlawful U.N. Security Council resolution, said North Korean Ambassador Han Tae Song.

Defense analysts at 38 North also reported on Wednesday that they detected new signs of activity at Punggye-ri, which suggests onsite work could now be changing focus to further prepare ... for future underground nuclear testing.