China warned Tuesday of "instability and uncertainty" on the Korean Peninsula as North Korea's unpredictable regime has claimed breakthroughs in its nuclear and missile capabilities.

"The Korean Peninsula and Northeast Asia are shrouded in instability and uncertainty," the State Council, the Cabinet of the communist-ruled nation, said in its latest defense policy paper.

The 25-page paper did not elaborate on North Korea, but along with an array of security tensions with its neighbors, including the South China Sea, the Korean Peninsula issue poses "a negative impact on the security and stability along China's periphery," the paper said.

North Korea has claimed that it successfully test-launched a ballistic missile from a submarine and made a breakthrough in miniaturizing nuclear warheads.

If confirmed, it would pose a significant security threat to South Korea and the region.

The paper also criticized Japan for trying to allow the Japanese military to fight abroad.

"Japan is sparing no effort to dodge the post-war mechanism, overhauling its military and security policies. Such developments have caused grave concerns among other countries in the region," it said.

China's massive land reclamation project in the South China Sea has made its Asian neighbors nervous. The U.S. has been concerned about China's increasingly assertive moves in the South China Sea, which is resource-rich and includes key shipping lanes.

China claims sovereignty over nearly 90 percent of the South China Sea, worsening relations with neighbors such as the Philippines, Malaysia and Vietnam. Beijing is also in a bitter dispute with Tokyo over islets in the East China Sea.

Speaking to reporters after releasing the paper, Yang Yujun, a spokesman for China's defense ministry, defended the reclamation work in the South China Sea.

"Our responses are always necessary, legal and professional," Yang said.

In a thinly-veiled criticism against the U.S., the paper said, "Some external countries are also busy meddling in South China Sea affairs; a tiny few maintain constant close-in air and sea surveillance and reconnaissance against China." (Yonhap)