SEOUL, Dec 20 (AFP) - North Korea on Tuesday denounced Japan's new security strategy as fundamentally changing the regional security environment and warned it will show how "wrong" and "dangerous" Japan's choice is with unspecified actions, official news agency KCNA reported.

A North Korean foreign ministry spokesperson made the remarks in a statement carried by KCNA, days after Japan unveiled its biggest military build-up since World War Two as regional tension and Russia's Ukraine invasion stoke war fears.

"Japan is bringing a serious security crisis on the Korean Peninsula and in the East Asia region by adopting a new security strategy that effectively acknowledges its pre-emptive strike capabilities against other countries," the official said in the statement.

The security environment in the region has "fundamentally changed" due to Japan's new policy, the official said, denouncing the move as a violation of the U.N. Charter and a "serious challenge" to international peace.

"We make it clear once again that we have the right to take bold and decisive military measures to protect our fundamental rights ... in response to the complicated regional security environment," the official said.

"Japan will soon learn with a shudder it has made a clearly wrong and very dangerous choice."

Tokyo's sweeping, five-year plan, once unthinkable in pacifist Japan, will make the country the world's third-biggest military spender after the United States and China, based on current budgets.