North Korea conducted its fifth nuclear test on Friday, setting off a blast that was more powerful than the bomb dropped on Hiroshima, and said it had mastered the ability to mount a warhead on a ballistic missile.

Its most powerful explosion to date follows a test in January that prompted the UN Security Council to impose tightened sanctions that increased North Korea's isolation but failed to prevent it from accelerating weapons development.

Prime Minister Justin Trudeau joined a chorus of condemnation, calling the test a threat to the region's stability and an "unacceptable violation" of UN Security Council resolutions.

Minister of Foreign Affairs Stéphane Dion also released a statement Friday saying that the test was a direct threat to international security. "Canada condemns in the strongest terms North Korea's announced detonation of a nuclear warhead," Dion said. "We call upon North Korea to comply with its international obligations, take concrete steps toward denuclearization and re-engage in meaningful negotiations for a peaceful political solution."

Dion expressed support for South Korea and Japan, saying Canada "will examine further actions, in concert with the international community, in response to North Korea's behaviour."

International reaction

South Korean President Park Geun-hye said North Korean leader Kim Jong-un was showing "maniacal recklessness" in completely ignoring the world's call to abandon his pursuit of nuclear weapons.

The policy is at an impasse. — Prof . Tadashi Kimiya , Tokyo University

U.S. President Barack Obama said the test would be met with "serious consequences" and held talks with Park and Japanese Prime Minister Shinzo Abe, the White House said.

China, North Korea's only major diplomatic ally, said it was resolutely opposed to the test and urged Pyongyang to stop taking any actions that would worsen the situation.

Foreign Ministry spokeswoman Hua Chunying said China would lodge a diplomatic protest with North Korea at its embassy in Beijing for conducting the test.

China's official Xinhua news agency, in a commentary after North Korea confirmed the test, said it was shocking and unwise and would only "add oil to the flames."

But it added that nobody benefited from chaos or war in Korea, and all parties in the international community should exercise restraint and avoid doing anything that is "mutually irritating."

The Security Council — at the behest of the U.S., Japan and South Korea — will hold a closed-door meeting this afternoon to discuss the situation.

UN Secretary General Ban Ki-moon admitted he's frustrated by North Korea's continued tests and flouting of UN resolutions.

"I simply do not understand why they are continuing," Ban, who previously served as South Korea's foreign minister, told reporters in New York City. Four of the North's five nuclear tests have occurred during his time as secretary general, a position he will leave at the end of this year.

"I regret that I have not been able to materialize all the wishes and aspirations of the international community," he said.

North Korea TV announcement on nuclear test 0:33

Series of tests

North Korea, which labels the South and the United States as its main enemies, said its "scientists and technicians carried out a nuclear explosion test for the judgment of the power of a nuclear warhead," according to a report from its official KCNA news agency.

North Korea conducted its fourth nuclear explosion in January and followed it up with a series of missile tests despite severe United Nations sanctions. On Monday, it fired three medium-range missiles during a G20 summit in neighbouring China that was attended by U.S. President Barack Obama and other world leaders.

North Korea said the test proved it is capable of mounting a nuclear warhead on a medium-range ballistic missile.

Its claims of being able to miniaturize a nuclear warhead have never been independently verified.

North Korea has been testing missiles at an unprecedented rate this year, and the capability to mount a nuclear warhead on a missile is especially worrisome for its neighbours South Korea and Japan.

"The standardization of the nuclear warhead will enable the DPRK to produce at will and as many as it wants a variety of smaller, lighter and diversified nuclear warheads of higher strike power," North Korea's news agency said, referring to the country's formal name, the Democratic People's Republic of Korea.

Japan PM reacts to nuclear test 0:17

Grave threat

Japan Defence Minister Tomomi Inada said the Pyongyang regime's advances in mobile ballistic missile technology posed a grave threat to Japan.

North Korea's nuclear test coincided with the anniversary of its 1948 foundation as a republic.

Its continued testing despite sanctions presents a severe challenge to Obama in the final months of his presidency and could become a factor in the U.S. presidential election in November.

"Sanctions have already been imposed on almost everything possible, so the policy is at an impasse," said Tadashi Kimiya, a University of Tokyo professor specialising in Korean issues.

"In reality, the means by which the United States, South Korea and Japan can put pressure on North Korea have reached their limits," he said. Japan's Abe said such a nuclear test could not be tolerated.

'Not a happy day'

Japan's foreign minister lodged a protest and Tokyo also sent two military jets to begin measuring for radiation.

China's environment ministry began emergency radiation monitoring along its borders with North Korea in northeast China, state television reported.

Jeffrey Lewis of the California-based Middlebury Institute of International Studies said the highest estimates of seismic magnitude suggested this was the most powerful nuclear test conducted by North Korea so far.

He said the seismic magnitude and surface level indicated a blast with a 20- to 30-kilotonne yield. Such a yield would make this test larger than the nuclear bomb dropped by the United States on the Japanese city of Hiroshima in World War Two and potentially bigger than that dropped on Nagasaki soon after.

"That's the largest DPRK test to date … Not a happy day," Lewis told Reuters.

"The important thing is that five tests in, they now have a lot of nuclear test experience. They aren't a backwards state anymore," he said.