Addressing Japan’s parliament, Prime Minister Shinzo Abe has condemned North Korea’s reported test of a hydrogen bomb as a threat to his country’s safety.

North Korea's nuclear test is a serious threat to our nation's security and absolutely cannot be tolerated

Tokyo has pledged a tough response and is reaching out to other members of the international community.

“North Korea’s nuclear test is a serious threat to our nation’s security and absolutely cannot be tolerated,” Abe told deputies.

“We strongly denounce it.”

“Japan will firmly respond to this, including at the UN Security Council, in cooperation with the United States, South Korea, China and Russia.”

South Kora’s defence ministry said the country’s armed forces are stepping up their monitoring of North Korea.

In China, the Xinhua state news agency said that a test of a nuclear bomb by North Korea runs counter to the goal of denuclearisation and warned that any practice that disrupts stability in northeast Asia is ‘undesirable and unwise’.

If test reports are true, British Foreign Secretary Philip Hammond said Pyongyang would have committed a “provocation which I condemn without reservation“ .

Hammond tweeted the statement during a two-day trip to Beijing.

If North Korean H-bomb test reports are true, it is a grave breach of #UNSC resolutions & a provocation which I condemn without reservation — Philip Hammond (@PHammondMP) 6 Janvier 2016

The UN Security Council is set to hold an emergency meeting later on Wednesday. Efforts may follow to expand existing UN sanctions against North Korea.