The South Korean military assessed that North Korea improved the performance of its existing launch vehicle before firing cruise missiles on Wednesday.

At a press briefing on Thursday, the Joint Chiefs of Staff(JCS) responded to a question about the North's announcement that it tested the new strategic "Pulhwasal-3-31" cruise missile, saying the name appears to have changed.

Military authorities presumed the new missile to be an improved version of the previous "Hwasal-1" and "Hwasal-2" long-range strategic cruise missiles.

Noting that the missiles fired the previous day had a relatively shorter range compared to past cruise missiles, the JCS assessed that the latest test was aimed at improving the performance of existing missiles.

While Seoul tracked Wednesday's missiles in real time until they disappeared at the terminus, JCS said intelligence authorities in the South and the U.S. are analyzing details, including a possible mock test of strategic nuclear warhead detonation in mid-air.