South Korea's government of President Lee Myung-bak is a "disturber of peace in northeast Asia," a North Korean government institute said.

The Disarmament and Peace Institute, part of the North Korean Foreign Ministry, said the Lee administration, after four years in office, has been fomenting discord in the region, a report by the government-run Korean Central News Agency said.

Lee has put north-south relations "at their lowest ebb, placing peace and security in northeast Asia at serious peril and creating a stumbling block in the process of denuclearization."

The DPI report -- another in a line of similar reports from the DPI criticizing South Korea and Lee -- also blames the United States for destabilizing inter-Korean relations by embarking on military maneuvers at a time of heightened tension.

Japan, too, has been drawn into an anti-North Korea alliance, especially after North Korea was blamed for the sinking of the South Korean navy patrol ship Cheonan in March 2010.

The Lee government "doggedly refused" to allow an inspection group from North Korea's National Defense Commission to investigate the sinking, Pyongyang claims.

It was against this backdrop that the United State staged military drills with South Korea, games North Korea alleged included forces capable of being turned into an invasion force.

"The number of U.S.-South Korean joint military maneuvers and drills sharply increased and a triangular military alliance of the United States, South Korea and Japan took clear shape, arousing distrust of neighboring countries," the report said.

Lee remains "obsessed with the pipe dream of achieving unification through absorption." He also "pushed the peninsula into a touch-and-go situation where the North and the South fired shells at each other for the first time since war that broke out in 1950."

Seoul media reported the incident, in November 2010, saying the North unexpectedly shelled South Korea's Yeonpyeong Island, killing two South Korean marines and two civilians. The South returned fire.

North Korea's shelling was believed to have been a response to South Korean military exercises in the politically sensitive sea area. Yeonpyeong Island is less than 8 miles from the North Korean mainland.

Yeonpyeong lies near the Northern Limit Line, the sea boundary agreed to by both Koreas in the 1953 armistice that ended three years of open armed conflict. But North Korea increasingly has contested the agreement in the past 15 years.

Previous DPI reports have accused Lee and his government of similar actions. A report in September again called on the international community to urge South Korea to "wake up from the dangerous dream of unification through absorption."

The latest DPI report comes after reassurances at the end of December that North Korea would not change its stance toward South Korea, despite the death of President Kim Jong Il two weeks earlier and the accession to power in Pyongyang of his youngest son, Kim Jong Un.

North Korea's National Defense Committee said Seoul's "foolish politicians" are wrong if they think Pyongyang will drop its guard against South Korea.

"We declare solemnly and confidently that the foolish politicians around the world, including the puppet group in South Korea, should not expect any change from us," the NDC was quoted as saying.

Intense international speculation has surrounded the rapid rise to power of Kim Jong Un, of whom little is known. Even his exact age -- believed to be 27 or 28 -- is unclear.

The role of China with regards to inter-Korean relations remains of the highest importance for both North and South Korea. China is one of few backers of North Korea and also has had a calming effect diplomatically on Pyongyang's anti-South Korea rhetoric.

South Korea sees China as a key player because of its perceived ability to rein in any overly aggressive North Korean military acts, on land and on sea, in an effort to maintain peace in the northeast Asia region.

Earlier this month Lee was in Beijing for a three-day state visit during which he met with Chinese President Hu Jintao and National People's Congress Chairman Wu Bangguo. It was the first major meeting between the two since North Korean leader Kim Jong Il's death.

A statement issued by Lee's office said Lee and China's leaders were to "discuss ways to develop the strategic partnership between the two nations and co-operative measures for peace and stability on the Korean Peninsula."

Discussions included increased trade between China and South Korea, which could lead to a free-trade agreement, the BBC reported.