North Korea test-fires strategic cruise missiles from submarine

North Korea test-fired two strategic cruise missiles from a submarine on Sunday, state news agency KCNA said on Monday just as U.S.-South Korea military drills were due to begin.

"Strategic" is typically used to describe weapons that have a nuclear capability. KCNA said the launch confirmed the reliability of the system and tested the underwater offensive operations of submarine units that form part of North Korea's nuclear deterrent.

South Korea's Joint Chiefs of Staff said the military was on high alert and the country's intelligence agency was working with its U.S. counterpart to analyze the specifics of the launch.

On Monday, South Korean and American troops were scheduled to begin 11 days of joint drills, dubbed "Freedom Shield 23."

The submarine launches aimed to show North Korea's determination to control a situation in which, KCNA said, "the U.S. imperialists and the south Korean puppet forces are getting evermore undisguised in their anti-DPRK military manoeuvres."

DPRK stands for North Korea, officially the Democratic People's Republic of Korea.

KCNA said the strategic cruise missiles were fired from the "8.24 Yongung" submarine in the water off the east coast of Korea in the early hours of Sunday.

The missiles traveled some 1,500 kilometres before hitting a target in the sea, the KCNA report said.