The White House said Thursday it doubts North Korean leader Kim Jong-un's claims that the communist nation has developed hydrogen bombs.

"We certainly are concerned about the policies and intent and destabilizing actions of the North Korean regime. At this point, you know, the information that we have access to calls into serious question those claims," White House spokesman Josh Earnest said at a regular briefing of the North's H-bomb claims.

"But we take very seriously the risks and the threat that is posed by the North Korean regime and their ambitions to develop a nuclear weapon that doesn't just threaten our close allies in South Korea, but could have a pretty destabilizing impact and even a national security threat to other countries in the region," he said.

According to Pyongyang's state media, the North's leader said the country has become a "powerful nuclear weapons state ready to detonate a self-reliant A-bomb and H-bomb to reliably defend its sovereignty and the dignity of the nation."

It was believed to be the first time that Kim has publicly mentioned the North's development of an H-bomb, which uses more advanced technology and is considered much more powerful than conventional nuclear weapons based either on weapons-grade plutonium or highly enriched uranium.

The State Department urged the North to completely give up all of its nuclear weapons and programs.

"We continue to call on North Korea to comply with its international commitments and obligations. North Korea must abandon all nuclear weapons and existing nuclear programs in a complete, verifiable and irreversible manner, and cease all related activities immediately," State Department spokeswoman Katina Adams told Yonhap News Agency.

"The international community stands united in its firm opposition to North Korea's development of nuclear weapons. North Korea will not achieve the prosperity and security it seeks and will remain isolated until it abandons its illicit weapons programs and abides by its international obligations and commitments," she said.

South Korea's intelligence community was skeptical about the North's H-bomb capability, with an intelligence official saying that the North is not believed to have such capabilities when it has not yet mastered the technology to miniaturize nuclear warheads.

In Beijing, China said it is aware of the North's H-bomb claim, and called for all relevant countries to make greater efforts to denuclearize the Korean Peninsula, lower tensions and maintain peace and stability.

North Korea has conducted three underground nuclear tests so far, in 2006, 2009 and 2013. The country has also conducted a series of long-range missile or rocket launches since 1998. In its most recent launch in late 2012, the North succeeded in putting a satellite into orbit.

Analysts have warned that it is only a matter of time until the North develops nuclear-tipped missiles. Some experts have recently warned that the communist nation's nuclear arsenal could expand to as many as 100 bombs by 2020.

The six-party talks aimed at resolving the North Korean standoff have been stalled since late 2008. North Korea demands the unconditional resumption of negotiations, while the U.S. says that Pyongyang must first take concrete steps demonstrating its denuclearization commitments. (Yonhap)