North Korea has now developed a hydrogen bomb and can use it along with nuclear warheads to defend its sovereignty, the country's central news agency has reported.

“We managed to become a great nuclear power capable of defending the independence and national dignity of our homeland by mighty nuclear and hydrogen strikes,” leader Kim Jong-un was quoted as saying by the central news agency. He also said North Korea “has to continue with actively developing its military industry.”

N Korea threatens to ‘invade US’ unless S Korean military exercises aren’t halted http://t.co/xUQGDqgfWfpic.twitter.com/F7NPuR53Hq — RT (@RT_com) August 16, 2015

The statement came as Kim Jong-un was on a tour inspecting an upgraded arms plant in Pyongyang on Thursday, according to TASS quoting the N. Korean central news agency.

So far it has not been confirmed that the country has in fact designed and created a hydrogen bomb.

Indeed, the South Korean intelligence community and experts say North Korea is unlikely to have enough scientific know-how to design a H-bomb.

"We don't have any information that North Korea has developed a H-bomb," an intelligence official from South Korea’s National Intelligence Service (NIS) told Yonhap news agency. "We do not believe that North Korea, which has not succeeded in miniaturizing nuclear bombs, has the technology to produce a H-bomb."

"It's hard to regard North Korea as possessing a H-bomb. I think it seems to be developing it," research fellow at Seoul-based Science and Technology Policy Institute Lee Chun-geun was quoted as saying by Yonhap.

On February 10, 2005 North Korea declared it had created nuclear weapons. The announcement was widely condemned by the international community. The country has since conducted underground nuclear tests three times, in 2006, 2009 and 2013.

Read more

The three nuclear tests are said to be critical for North Korea’s strategic arms program. The first known underground nuclear test was conducted in 2006 at the Punggye-ri Nuclear Test Site in the northeast of the country. It was recorded by seismic stations in Russia, China, Japan, South Korea and Australia. According to rough estimates, a nuclear device of 5 to 10 kilotons of TNT was exploded.

The second and third tests were conducted in May 2009 and January 2013 respectively, prompting international condemnation and unilateral sanctions by the US for violating the non-proliferation regime. The estimated power of the devices tested was 10 to 20 kilotons of TNT each.

In 2013, the UN Security Council unanimously imposed new sanctions against North Korea for its latest nuclear test, which came hours after Pyongyang threatened a pre-emptive nuclear strike against the US and South Korea in March of that year. The sanctions involve penalties on the country’s banking, travel and trade.

A hydrogen bomb is a nuclear weapon of mass destruction that uses energy from a primary nuclear blast to ignite a secondary nuclear fusion, and is by far the most powerful weapon on earth. The first country to build a H-bomb was the Soviet Union, whose AN602 hydrogen bomb (often referred to as the 'Tzar Bomb') was tested in 1961.