The North's leader Kim Jong Un oversaw the test-launch from a location off-shore as the submarine dove under water and "a ballistic missile surfaced from the sea and soared into the air, leaving a fiery trail of blaze," the official KCNA news agency said.
"Through the test, it was verified and confirmed that the underwater ballistic missile launch from a strategic submarine fully achieved the latest military, scientific and technical requirements," KCNA said.
North Korea is under United Nations sanctions banning it from developing or using ballistic missile technology.