Pyongyang’s official Korean Central News Agency said the missiles were launched during a drill of a “railway-borne missile regiment” that transported the weapons system along rail tracks in the country’s mountainous central region and accurately struck a sea target 800 kilometers (500 miles) away.
State media showed what appeared to be two different missiles streaking up from rail-car launchers engulfed in orange flames along tracks surrounded by dense forest.
A rail-based ballistic system reflects North Korea’s efforts to diversify its launch options, which now includes various vehicles and ground launch pads and may eventually include submarines.
Firing a missile from a train could add mobility, but some experts say North Korea’s simple rail networks running through its relatively small territory would be quickly destroyed by enemies during a crisis.
It comes after the two Koreas test-fired missiles hours apart in dueling displays of military might. The launches underscored a return of the tensions between the rivals amid a prolonged stalemate in US-led talks aimed at stripping North Korea of its nuclear weapons programme.
“Our military assesses that North Korea is continuously developing various mobile launch equipment,” said Colonel Kim Jun-rak, a spokesman for South Korea's Joint Chiefs of Staff. He said the South Korean and US militaries were continuing to examine the North’s launches.
North Korean leader Kim Jong Un vowed at a party congress in January to bolster his nuclear deterrent in the face of US-led sanctions and pressure.
He issued a long wish list of sophisticated weaponry, including longer-range intercontinental ballistic missiles, nuclear-powered submarines, spy satellites and tactical nuclear arms.
In another weapons display over the weekend, the North said it tested new cruise missiles, which it intends to make nuclear-capable, that can strike targets 1,500 kilometers (932 miles) away, a distance putting all of Japan and US military installations there within reach.
Hours after the latest North Korean launches, South Korea reported its first test of a submarine-launched ballistic missile. As President Moon Jae-in and other top officials watched, the missile flew from a submarine and hit a designated target, the president’s office said.
Kim Yo Jong, the powerful sister of the North Korean leader, threatened a “complete destruction” of bilateral relations over Mr Moon's comments while he observed the test, when he said the South’s growing conventional missile capacities would be a "sure deterrence" against North Korean provocation.