The South Korean Navy has retrieved three more pieces of debris from North Korea's long-range rocket on the west coast, Seoul's defense ministry said Sunday, hoping they would provide more knowledge about the communist nation's missile technology.

Pyongyang fired off a three-stage "Unha 3" rocket on Dec. 12, claiming that it has succeeded in putting a satellite into orbit.

The first stage of the rocket fell into the Yellow Sea off South Korea's west coast and the second stage in waters near the Philippines.

After the Navy collected the upper part of the first stage two days after the firing, it salvaged three more pieces from its lower part, which included a fuel tank inscribed with the number "3," a combustion chamber and an engine connection rod, the ministry said.

A minesweeper equipped with the sonar system detected the parts in waters 151 kilometers west of the southwestern city of Gunsan and 85 meters below the sea, it said.

"As the additional pieces are salvaged, we will be able to look deeper into the function and structure of North Korea's long-range rocket," a senior ministry official said.

With the latest finding, Seoul has collected key components of the first-stage, except for the engines.

After examining the 3.2-ton wreckage with the sign "Unha" written in Korean on it, a joint investigation team on Sunday concluded that the wreckage is an oxidizer container, which stored red fuming nitric acid, to fuel the rocket's first-stage propellant.

The storable oxidizer that contains highly toxic chemicals is used by missiles developed by the Soviet Union, which is rarely used by countries with advanced space technology, the team concluded.

The South Korean findings reinforced suspicions voiced by the U.S. and other Western allies that the North's rocket launch was intended to test its inter-continental ballistic missile technology in violation of U.N. resolutions. (Yonhap)