North Korea poses a bigger threat than Islamic State, an Australian nuclear weapons expert says.

RMIT University Professor Joe Siracusa says the world has become more uncertain and dangerous since North Korea’s announcement that it had conducted a “successful” underground hydrogen bomb test.

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“The North Koreans can create more damage in about three hours than ISIS can in 30 years,” he told 3AW on Thursday.

“They have thousands of rockets, they have launchers, they have everything you need to create a nuclear nightmare.”

Professor Siracusa said the dangerous development had taken the world by surprise.

North Korea had been on an “atomic spending spree”.

“This is the only thing they have that the world is really interested in,” he said.