On Wednesday, South Korean and Japanese authorities said they had detected the launch of two ballistic missiles from North Korea
The missiles fired by North Korea on Wednesday were a test of a new "railway-borne missile system" designed as a potential counter-strike to any forces that threaten the country, state news agency KCNA reported on Thursday.
The missiles flew 800km before striking a target in the sea off North Korea's east coast, KCNA said.
On Wednesday, South Korean and Japanese authorities said they had detected the launch of two ballistic missiles from North Korea, just days after it tested a cruise missile that analysts said could have nuclear capabilities.
The North Korean launches came the same day that South Korea tested a submarine-launched ballistic missile (SLBM), becoming the first country without nuclear weapons to develop such a system.
The two Koreas have been in an increasingly heated arms race, with both sides unveiling more capable missiles and other weapons.
The tests by nuclear-armed North Korea drew international condemnation and concern, however, with the United States saying they violated UN Security Council resolutions and posed a threat to Pyongyang's neighbours.
North Korea has been steadily developing its weapons systems, raising the stakes for stalled talks aimed at dismantling its nuclear and ballistic missile arsenals in return for US sanctions relief.
The North Korean test was conducted by a railway-borne missile regiment that had been organised earlier this year, the KCNA report said.