North Korea's state-run Korean Central News Agency (KCNA) said on Monday that leader Kim Jong Un oversaw the test of a missile called "Pulhwasal-3-31", which resembles a strategic cruise missile that North Korea said last week was under development.

Also according to KCNA and North Korea's official newspaper Rodong Sinmun, the missiles flew over the sea off the country's east coast for about 7,445 seconds and hit an unidentified target on an island, thus the flight time exceeded two hours.

KCNA quoted Mr Kim Jong Un calling the test a success and saying it "has strategic significance in implementing the plan... to modernize the army to build a powerful navy".

Earlier on Sunday, the South Korean military said North Korea had fired multiple cruise missiles off its coast. Last week, North Korea tested a new strategic cruise missile, but did not mention that it was being developed for submarine launch.

State media photos released on Monday showed a rocket launching into cloudy skies from the water, leaving a plume of smoke obscuring the launch pad.

North Korea's cruise missiles are not banned under UN Security Council resolutions. However, analysts say intermediate-range cruise missiles pose as much of a threat as ballistic missiles.

In recent months, North Korea has tested a range of new and advanced weapons, including advanced ballistic missile systems and underwater drones.

KCNA said Kim Jong Un personally inspected the construction of the submarine and issues related to the production of other new warships. North Korea launched its first attack submarine last year, capable of carrying ballistic and cruise missiles.

Huy Hoang (according to KCNA, Yonhap, Reuters)