North Korea has tested an engine for its long-range missiles at a new launch base under construction in Dongchang-ni, North Pyeongan Province.

A government source says the launch base is about 80 percent complete and its engine test facility is already operational. The source said the North appeared to have conducted the test in May or June.

Satellite pictures that captured the blackened ground after the test suggest the rocket engine was for a long-range missile.

The source said Pyongyang seemed to be working to improve the engine of Daepodong-2 ballistic missiles, which U.S. intelligence believes have a maximum range of six-thousand kilometers. In 2006, the North unsuccessfully test-fired the long-range missile.