BEIJING -- The United Nations Security Council has announced an emergency meeting after North Korea carried out its fifth nuclear test over night. The country claims it’s now able to arm its ballistic missiles with nuclear warheads, and while that’s likely still an ambition, the test is raising serious concerns.

A 5.3-magnitude tremor, detected in a remote area of North Korea, was the first sign of the test, and it triggered rapid international condemnation.

President Obama -- returning from a trip to Asia -- said there would be “serious consequences.”

In a statement released later Friday, Mr. Obama said the U.S. condemned the nuclear test “in the strongest possible terms as a grave threat to regional security and to international peace and stability.”

“North Korea stands out as the only country to have tested nuclear weapons this century,” added the president.

As CBS News correspondent Adriana Diaz reports, it was the North’s second nuclear test this year, and it comes just after the U.S. and South Korea held joint military exercises last month. The U.S. is also advancing with plans for a missile defense shield on the Korean Peninsula.

All of those factors have angered the North and its increasingly-isolated leader Kim Jong Un, and the test will only further complicate an already-tense situation.

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North Korea said overnight the test was performed on a “newly-developed nuclear warhead” at a remote site used for previous nuclear tests.

“The standardization of the nuclear warhead will enable (North Korea) to produce at will and as many as it wants a variety of smaller, lighter and diversified nuclear warheads of higher strike power with a firm hold on the production of various fissile materials and technology for their use. This has definitely put on a higher level (the North’s) technology of mounting nuclear warheads on ballistic rockets,” the North’s state-run media announced.

Hours after the test, South Korean officials scrambled together an emergency meeting. On his way back from Asia, President Obama consulted with the South’s President Park Geun-hye and Japanese Prime Minister Shinzo Abe in separate phone calls.

White House Press Secretary Josh Earnest said Mr. Obama would continue close consultations with allies in the region “to ensure provocative actions from North Korea are met with serious consequences.”

Later Friday morning, the White House released a full statement from the president, saying “the United States does not, and never will, accept North Korea as a nuclear state.

“Far from achieving its stated national security and economic development goals, North Korea’s provocative and destabilizing actions have instead served to isolate and impoverish its people through its relentless pursuit of nuclear weapons and ballistic missile capabilities.”

President Park said the test demonstrated the “fanatic recklessness of the Kim Jong Un government as it clings to nuclear development.”

The test violates five U.N. Security Council resolutions, and more practically it threatens to greatly undermine regional stability.

Mr. Obama, in the statement released by the White House, called it a “flagrant violation” of U.N. Resolutions, which makes “clear North Korea’s disregard for international norms and standards for behavior and demonstrates it has no interest in being a responsible member of the international community.“

China issued a statement Friday urging the North Koreans to adhere to their nuclear non-proliferation promises, and chastizing the Kim regime for its “disregard” for international objections.

“Today, the DPRK (North Korea) again conducted a nuclear test despite widespread international opposition,” Chinese Foreign Ministry spokeswoman Hua Chunying said at a briefing. “We strongly urge the DPRK to honour its commitment to denuclearization, comply with the relevant Security Council resolutions, act cautiously, and stop taking any actions that worsen the situation. Any actions solely in one side’s interest will only escalate the situation.”

Pyongyang had already caused concern earlier this week by launching three missiles while China was hosting world leaders at the G-20 summit.

On Thursday, at a regional summit in Laos, President Obama condemned the launches, which he called “provocations,” after meeting with South Korea’s President Park.

“It is entirely fair to say that they have continued to engage in the development of their nuclear program and these ballistic missile tests. So we are constantly examining other strategies we can take,” Mr. Obama said, prior to Friday’s nuclear test.

But it remains unclear what action the Security Council might take now, and a lot depends on China, the North’s neighbor and only major ally -- though ties have frayed over the nuclear and missile tests in recent years.

After last week’s missile launches, China’s U.N. Ambassador Liu Jieyi told CBS News foreign affairs analyst Pamela Falk that it was “certainly” viewed as an aggressive message to Beijing, adding that the Council would respond promptly this time.

Falk says what the U.S., Japan, and South Korea feel is needed is strict enforcement of the existing U.N. resolution, which includes biting sanctions against the North. The Security Council issued a swift, but non-enforceable statement condemning those launches, as talks continued over what measures to take, to show North Korea that China was on board, and angry about Pyongyang’s continuing defiance.

In North Korea, the nuclear program is a source of national pride. When CBS News’ Diaz visited in May, the nation put on a major show of military hardware, on parade through the streets of the capital, to celebrate their first nuclear test of the year, on January 6.

Later that month, in a three-hour speech, Kim Jong Un pledged to use nuclear weapons only in self defense.

“We will not use nuclear weapons first,” he said, “unless aggressive hostile forces use them to invade our sovereignty.”

“Every time we condemn them, they come back at us with another test,” Joshua Pollack, an expert on nuclear and missile proliferation, tells CBS News. “That suggests that we are locked into this action-reaction cycle.”

“They are the only country right now that continues to test nuclear devices,” Pollack says, adding that he thinks “there is more to come… if you read their statements in last few days I think it has become increasingly clear they have more planned for us even before the end of this year.”