North Korea is believed to have conducted a test of a liquid propellant rocket engine in late April, a U.S. think tank said based on satellite imagery and knowledgeable sources.
The Center for Strategic and International Studies said Monday the unannounced test was carried out during the fourth week of April at the Yunsong vertical engine test stand within the Sohae Satellite Launching Station.
The Washington-based think tank said the test is a clear indication North Korea is advancing its development of more sophisticated long-range ballistic missiles, space launch vehicles and satellites.
The imagery from April 29, disclosed by CSIS, showed traces of burned vegetation near the test stand.
In April, CSIS, as well as South Korean officials, said there were some signs North Korea could launch its second spy satellite by the end of the month, but it did not happen.
After two failures, North Korea placed its first military reconnaissance satellite into orbit in November last year from the launching station in Tongchang-ri in the country's northwest.
In addition to the Malligyong-1 satellite, North Korea plans to launch three more this year, leading U.S., Japanese and South Korean officials to closely monitor related activities.
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