The launch was the DPRK's fifth attempt since 1998. An April launch failed in the first of three stages, raising doubts among outside observers whether Pyongyang could fix what was wrong in eight months. But those doubts were erased on Wednesday.
The Unha rocket, Korean for "galaxy", blasted off from a launchpad northwest of Pyongyang just three days after the DPRK indicated that technical problems might delay the launch.
ROK navy ships found what appears to be debris from the first-stage rocket in the Yellow Sea and were trying to retrieve it on Thursday, defense officials said. The debris is believed to be a fuel container from the first rocket stage.
"A salvage operation is now under way to retrieve it," a Defense Ministry spokesman said, adding that Seoul has no plans to return it to Pyongyang because the launch violated UN resolutions.
The chunk of debris was found on the seabed, about 160 km west of the southwestern port of Gunsan, Yonhap news agency said, at a depth of around 80 meters.
Before its previous rocket launch attempt in April - which ended in failure - the DPRK had warned both Japan and the ROK that any effort to salvage debris from the rocket would be considered an "act of war".
But the warning was not repeated before Wednesday's launch.
The launch could leave Pyongyang even more isolated and cut off from much-needed aid and trade.
The UN imposed two rounds of sanctions after nuclear tests in 2006 and 2009, and ordered the DPRK not to conduct any launches using ballistic-missile technology. Pyongyang maintains its right to develop a civilian space program, saying the satellite will send back crucial scientific data.
AP-AFP