By RFE/RL

The international community has strongly condemned North Korea's latest nuclear weapons test, with China urging the secretive communist state to stop "wrong" actions and Russia saying it could lead to “serious consequences.”

North Korea said on September 3 that it successfully tested a hydrogen bomb capable of being loaded onto its long-range missiles -- in what was apparently its most powerful nuclear test yet.

State media said that Pyongyang's sixth nuclear test was a "perfect success" and was a "meaningful" step in completing the country's nuclear weapons program.

Japanese Chief Cabinet Secretary Yoshihide Suga said the test may have been of a hydrogen bomb "given the fact that the scale of tremor detected was the largest so far.”

A hydrogen bomb is more powerful than a regular atomic bomb -- like the ones the United States dropped on Japan near the end of World War II.

China, North Korea's only major ally, said North Korea "has ignored the international community's widespread opposition, again carrying out a nuclear test."

Beijing "expresses resolute opposition and strong condemnation toward this," the Foreign Ministry statement said.

U.S. President Donald Trump wrote on Twitter that Pyongyang's "words and actions continue to be very hostile and dangerous to the United States."

In a separate message, he described North Korea as "a rogue nation which has become a great threat and embarrassment to China, which is trying to help but with little success."

"Talk of appeasement" with North Korea will not work, he also wrote, adding, “They only understand one thing!"

Russia said the nuclear test “deserves the strongest condemnation" and called on all interested parties to “immediately return to dialogue.”

"It is imperative to remain calm and to refrain from any actions that lead to a further escalation of tension," a Foreign Ministry statement said, adding that North Korea risked "serious consequences."

South Korea said will seek every available measure, including new UN sanctions, to further isolate Pyongyang.

"In terms of our alliance with the United States, we will discuss deploying the most powerful U.S. strategic military assets [to the Korean Peninsula]," National Security Director Chung Eui-yong said said.

Japan's government said sanctions against North Korea should include restrictions on the trade of oil products.

French President Emmanuel Macron and German Chancellor Angela Merkel also called for tougher EU sanctions against North Korea, saying it has "reached a new dimension of provocation."

The director-general of the UN atomic watchdog, the Vienna-based International Atomic Energy Agency (IAEA), said North Korea's latest nuclear test was "extremely regrettable" and "in complete disregard" of the international community's repeated demands.

Pyongyang has conducted nuclear tests since 2006 in violation of United Nations resolutions.

It claimed its sixth nuclear test after North Korean state media claimed the country had successfully developed an advanced hydrogen bomb that could be loaded onto an intercontinental ballistic missile (ICBM).

Neither claim could be independently confirmed.

The official KCNA news agency said the hydrogen bomb was the country’s most-advanced nuclear weapon and has "great destructive power."

Following that announcement, seismologists detected a powerful earthquake in an area where North Korea had conducted previous tests.

The U.S. Geological Survey said it detected an earthquake of 6.3 magnitude at a depth of zero kilometers. Jana Pursely, a USGS geophysicist, told the AFP news agency that "it's an explosion rather than an earthquake."

The Chinese Earthquake Administration described the quake as a "suspected explosion." It detected a second quake minutes after the first, saying that it might be a "collapse earthquake," suggesting the rock over the underground blast had given way.

South Korean officials said that the “artificial earthquake” took place in Kilju County, where the North's Punggye-ri nuclear test site is situated.

"The scale of the energy was five to six times more powerful” than North Korea’s fifth nuclear test, which occurred in September 2016, according to Lee Mi-Sun, head of the South Korean meteorological agency.

Russian monitors said that radiation levels in the country’s Far East remained "in normal range" after Pyongyang said it tested a hydrogen bomb. "No excesses in background radiation levels were detected,” local state monitoring service Primgidromet said in a statement.

Before the indications of the possible nuclear test, White House and Japanese officials said Trump and Japanese Prime Minister Shinzo Abe had spoken by phone in the face of the "escalating" situation with North Korea.

The leaders were quoted as agreeing that close cooperation between their countries and South Korea was needed, along with increased pressure on Pyongyang.

Tensions between Pyongyang and many world powers, particularly the United States, Japan, and South Korea, were already at their highest levels in years.

Trump and Kim have exchanged threats in a war of words that intensified after Pyongyang test-launched two ICBM-class missiles in July that had a potential range of 10,000 kilometers – enough to hit many parts of the United States.

There had been speculation that the North could conduct another nuclear test on September 9, the anniversary of the founding of the country.

The United States and South Korea on September 1 said they agreed to strengthen Seoul's defenses, and Washington approved the sale of billions of dollars worth of arms to the South to counter the North.

Russian President Vladimir Putin, in an article published on September 1, said the standoff over North Korea's nuclear and missile programs is "on the verge of a large-scale conflict."

Putin indirectly criticized U.S. warnings of potential military action and said stepping up pressure on Pyongyang won't solve the problem, adding that the crisis can only be settled through “direct dialogue between all concerned parties, without preconditions."

With reporting by AFP, AP, Reuters, and dpa