North Korea fired an unidentified projectile off its east coast on Tuesday, South Korea's Joint Chiefs of Staff said, the latest potential missile launch by the nuclear armed state.

The JCS did not immediately elaborate, but such projectiles have often been ballistic missile tests by the North, which has pressed ahead with military development in the face of international sanctions imposed over its nuclear weapons and missile programmes.

The launch came as the intelligence chiefs of the United States, South Korea, and Japan were due to meet in Seoul to discuss the standoff with North Korea, amid other issues, Yonhap news agency reported, citing a government source.

The launch came as the intelligence chiefs of the United States, South Korea, and Japan were due to meet in Seoul to discuss the standoff with North Korea, amid other issues, Yonhap news agency reported, citing a government source.

Representatives of hundreds of international companies and international militaries were gathered in Seoul for the opening ceremonies of the International Aerospace and Defence Exhibition (ADEX).

It is set to be South Korea's largest defence expo ever, with displays of next-generation fighter aircraft, attack helicopters, drones, and other advanced weapons, as well as space rockets and civilian aerospace designs.