Republican members of Congress lambasted U.S. President Barack Obama's policy on North Korea as a "failure" after the communist nation stunned the world with claims that it has successfully conducted its first H-bomb test.

"The administration's North Korea policy has proven a dramatic failure, and we urgently need a new approach," Rep. Ed Royce, chairman of the House Foreign Affairs Committee, said in a statement.

"Dictators like Kim Jong-un don't take time outs, they take advantage when the U.S. looks away," he said. "As Iran prepares to gain billions in sanctions relief, North Korea surely thinks it can intimidate the Obama administration into the same."

Royce called for greater pressure on Pyongyang.

"This rogue regime has no interest in being a responsible state. It continues to starve its people while it works to advance nuclear, missile and cyber weapons that pose a direct threat to the U.S. and our allies," he said.

North Korea announced earlier Wednesday that it has successfully carried out a hydrogen bomb test, claiming that the test means "a higher stage of the DPRK's development of nuclear force" and that the country "proudly joined the advanced ranks of nuclear weapons states possessed of even an H-bomb."

The latest test marked the North's fourth nuclear test following three previous ones in 2006, 2009 and 2013. Three of the four tests happened while Obama was in office. The Obama administration has been accused of ignoring the North's nuclear problem as it's preoccupied with Middle Eastern issues.

"I have been warning throughout this campaign that North Korea is run by a lunatic who has been expanding his nuclear arsenal while President Obama stood idly by," Republican presidential hopeful and Sen. Marco Rubio said in a statement.

"If this test is confirmed, it will be just the latest example of the failed Obama-Clinton foreign policy," he said. "Our enemies around the world are taking advantage of Obama's weakness. We need new leadership that will stand up to people like Kim Jong-un and ensure our country has the capabilities necessary to keep America safe."

Sen. Cory Gardner (R-CO), chairman of the Senate Foreign Relations Committee's subcommittee on East Asia and Pacific affairs, also criticized the Obama administration for ignoring the problems, calling North Korean leader Kim Jong-un a "forgotten maniac" and "madman."

"Events like this are a symptom of a failed foreign policy. The Obama administration's stance on Russia, Syria, and especially Iran have sent a clear message to dictators and despots around the

world: if you act badly enough, for long enough, this administration will reward your behavior," Gardner said in a statement.

The senator also said that the testing of a hydrogen bomb would serve as a reminder of the danger posed to the world by "this often-forgotten maniac who leads a government that grips to power by fear, intimidation, and murder," he said.

Republican presidential front-runner Donald Trump said the North's nuclear program should be shut down before it's too late.

"You have this mad man over there who probably would use it and nobody talks to him, other than, of course, Dennis Rodman talked to him. That's about it. But nobody is talking to him whatsoever," Trump said on FOX News.

"We've got to close it down because he's getting too close to doing something. Right now, he's probably got the weapons, but he doesn't have the transportation system. Once he has the transportation system, he's sick enough to use it," he said.

Trump also called for greater efforts to get China to work harder to rein in the North, saying Beijing has "total control"

over the North. Unless China cooperates, the U.S. should make trade very difficult with China, Trump said.

Republican presidential hopeful and former Hewlett-Packard CEO Carly Fiorina also slammed the U.S. policy on the North as failure.

"Of course North Korea would conduct a nuclear test after watching Iran willfully violate an agreement they just made without consequence of any kind from this administration," she said in a Facebook message. "North Korea is yet another Hillary Clinton foreign policy failure. America cannot lead from behind."

Meanwhile, Democratic presidential front-runner and former Secretary of State Hillary Clinton called for increasing pressure on the North.

"North Korea's goal is to blackmail the world into easing the pressure on its rogue regime," Clinton said in a statement. "We can't give in to or in any way encourage this kind of bullying.

Instead, we should increase pressure and send Pyongyang an unmistakable message that its nuclear brinksmanship won't succeed."

Clinton also said that North Korea must have no doubt that the U.S. will "take whatever steps are necessary to defend ourselves and our treaty allies, South Korea and Japan."

She also said China "must be more assertive in deterring the North's irresponsible actions." (Yonhap)