North Korea carried out its June test of the Musudan intermediate-range ballistic missile from an east coast airport and is expected to use the facility for future tests, a U.S. website monitoring the North said.

The website 38 North said that the June 22 test took place at the Kalma International Airport in the city of Wonsan. The assessment was reached based on comparison of ground photos published by North Korean media and commercial satellite imagery, it said.

North Korea did not disclose where the test was carried out.

"This airport is in the final stages of being converted from the Wonsan Airbase to modern civilian facility, but also includes a recently constructed firing position for heavy missile transporter-erector-launchers," 38 North said.

"It is likely that North Korea will continue to use both this location and its companion facility on the Hodo Peninsula for live-fire artillery, rocket and missile tests, with the Kalma location being used primarily for highly publicized events and the Hodo facility for more routine testing and training," it said.

The June test clearly demonstrated the North is making significant progress in its intercontinental ballistic missile development as the Musudan missile reached space and then re-entered Earth's atmosphere before falling into targeted waters.

Re-entry technology has been considered one of the hardest obstacles the communist nation must overcome before developing a nuclear-tipped intercontinental ballistic missile, along with warhead miniaturization technology.

The launch was the North's sixth attempt to test the missile since April 15. All but the sixth launch failed, with the missiles exploding in midair or on a mobile launcher, or crashing seconds after launch. (Yonhap)