N. Korean leader Kim Jong-un says H-bomb test 'self-defensive'North Korean leader Kim Jong-un says its claimed hydrogen bomb test last week was an act of self-defense and a "fair action that nobody can criticize," the North's state media said Sunday.

The North claimed Wednesday it successfully conducted an H-bomb test for the first time, in defiance of United Nations' resolutions.

"The DPRK's H-bomb test, conducted at the outset of the year ... is a self-defensive step for reliably defending the peace on the Korean Peninsula and the regional security from the danger of nuclear war caused by the U.S.-led imperialists," Kim was quoted as saying by the North's state-run Korean Central News Agency.

DPRK is the acronym for North Korea's official name, the Democratic People's Republic of Korea.

He was speaking to the Ministry of People's Armed Forces at an event for the new year, the KCNA said.

South Korea and the U.S. say the blast observed last week is too weak to have originated from a full-fledged H-bomb.

South Korea estimates the yield of Wednesday's test to be 6 kilotons, while H-bombs typically yield dozens, if not hundreds, of kilotons, according to nuclear experts.

South Korea, Japan and the U.S. have said they will ramp up efforts to contain North Korea. China has also voiced its firm opposition to the North's test but denied responsibility in curbing its nuclear ambitions.

"The origin and frictions of the North Korean nuclear issue do not lie in China. The key to resolving the issue does not lie in China," Chinese foreign ministry spokeswoman Hua Chunying said.

On Friday, South Korea restarted its loudspeaker broadcasts against the North, which had been halted for about four months.

South Korea had broadcasted anti-North messages along the inter-Korean border after an explosion of a land mine planted by the North maimed two South Korean soldiers in August.

The broadcasts were stopped after the two sides reached a rare agreement to diffuse military tensions on the peninsula later that month. (Yonhap)