North Korea warned today that it might begin producing nuclear weapons, as alarm bells rang over its firing of a missile into the Sea of Japan.

Defending its decision to pull out of a key nuclear arms treaty, Pyongyang said that "at this stage" its nuclear activities would be confined to peaceful purposes.

North Korea's number two leader, Supreme People's Assembly president Kim Yong Nam, told the summit of the Non-Aligned Movement (NAM) here that the nuclear crisis had been caused by threats from the United States.

His remarks came a day after Pyongyang's firing of a missile ratcheted up regional tension, sparking a military alert in South Korea and criticism at the summit.

A South Korean defense ministry official said there were no details immediately available about the type of missile fired, or about its range.

North Korea agreed to a moratorium o­n missile testing after it caused international alarm in 1998 when it test-fired a Taepodong ballistic missile that flew over northeastern Japan into the Pacific Ocean.