The North fired three KN-01 missiles from a site near its eastern city of Wonsan, a ministry spokesman told AFP.
"The missiles appear to have a range of nearly 100 kilometres," he said, adding the test lasted 26 minutes and began around 4.30 pm.
"We are closely monitoring the movements of the North's military and maintaining full readiness against potential provocations," he said.
The test is the latest since Pyongyang claimed on May 9 it had successfully test-fired a SLBM -- a technology that could eventually offer the nuclear-armed state a survivable second-strike capability.
But some experts have questioned the authenticity of the May test, saying photos of the launch might have been digitally manipulated.