"It's assessed that there was meaningful progress in engine efficiency with the test," a ministry official told reporters, saying it reflects the ministry's official assessment.

He added that the North's newly unveiled equipment seems to have one main engine with four back-up ones connected.

He also took note of Pyongyang's assertion that it has improved the "non-propulsion" system.

"It is construed as meaning higher engine efficiency," he said. "(We) will have to closely monitor how the rocket engine will be used down the road."

The ministry's announcement was quite unusual, given its characteristically cautious public statements in response to the North's claims of its missile and nuclear capabilities.

The North's leader Kim Jong-un inspected the test conducted at the Sohae Satellite Launching Ground on Saturday, according to the Korean Central News Agency. The South calls the venue the Dongchang-ri site especially for the launch of intercontinental ballistic missiles.

The KCNA quoted Kim as saying, "The success made in the current test marked a great event of historic significance as it declared a new birth of the Juche-based rocket industry." Juche means self-reliance. (Yonhap)