The North has denied allegations that its Unha-3 rocket, launched Dec. 12, had any military purpose, insisting that it was purely for scientific research, The International Herald Tribune reported.
However, South Korean technicians scrutinizing the debris from the North's rocket launch said they found evidence suggesting the rocket's military purposes.
"They efficiently developed a three-stage long-range missile by using their existing Rodong and Scud missile technology," a senior military intelligence official said on Sunday, on the condition of anonymity.
The official also said the rocket used red fuming nitric acid, commonly used as rocket propellant in old Soviet-built Scud missiles, as well as Iranian and North Korean missiles, as an oxidizer, not liquid oxygen, which most space-program rockets use.
This suggested an "Iran connection" in North Korea's rocket program, he said.
Authorities found the welding on the oxidizer tank to be "crude," "uneven" and "done by hand," the official said.