Recent satellite imagery has shown new activity at North Korea's rocket launch site since last month's long-range missile launch, including possible preparations for a rocket engine test, a North Korea-monitoring website said Thursday.

The website 38 North said the imagery showed "an unusual convoy of five small four-meter-long trucks" traveling from the vertical engine test stand at the North's Dongchang-ri site, and the vehicles are believed to be returning from the delivery of supplies, fuel or even engine components.

"In addition to activity at the test area, vehicles and personnel are present at the Sohae launch pad. Their purpose, however, appears to be post-launch maintenance rather than preparations for a new satellite launch," the website said.

On Feb. 7, the North launched a long-range rocket that succeeded in putting a satellite into orbit.

North Korea says its rocket launches are aimed at putting satellites into orbit, claiming it has the right to the peaceful use of space. But Pyongyang is banned from such launches under U.N. Security Council resolutions as it has been accused of using them as a cover for testing intercontinental ballistic missiles.

Experts say long-range rockets and ICBMs are basically the same with differences only in payloads. (Yonhap)