South Korea's defense chief said there was successful separation of the first and second stages of North Korea's long-range rocket that was launched on Wednesday.

 "South Korea and the U.S. military are checking whether North Korea's rocket accurately entered orbit," Kim Kwan-jin told a Yonhap News reporter on his way back from an emergency national security meeting convened by President Lee Myung-bak. "Our radar has verified that (the rocket's) second stage separated."

Kim said his government was waiting for the analysis of the third stage from related organizations to verify Pyongyang's announcement that the rocket successfully put a scientific satellite into orbit.

Whether his military was ready for the Wednesday launch, Kim said, "We were always preparing." The launch was a surprise as the North had indicated technical problems with the rocket and recently extended its launch window to Dec. 29.

Following the launch shortly before 10 a.m., Seoul's defense ministry said one part of the rocket fell into waters west of the Korean Peninsula and another part fell in the sea east of the Philippines.

"North Korea fired off a long-range missile from the Dongchang-ri launch pad, and it was immediately detected by Aegis ships in the Yellow Sea," defense ministry spokesman Kim Min-seok said in a news conference. "We are currently analyzing whether it was successful."

The three-stage rocket was launched at 9:51 a.m. from the country's northwestern region, and its first stage was separated at 9:52 a.m. The first stage passed over the northernmost island of Baengnyeong one minute later and flew west of Japan's Okinawa at around 9:58 a.m., Kim said.

The ministry will make an announcement later in the day on whether the rocket launch was successful and American ambassador Sung Kim will visit the ministry, officials said.

The South Korean military is currently searching for rocket debris and has stepped up the military's readiness posture and upgraded its alert status.

The North says the Unha-3 rocket is aimed at putting a satellite in orbit, but South Korea, the U.S. and other nations see the launch as a cover for a test of ballistic missile technology that violates several U.N. resolutions.

A similar launch in April broke apart shortly after lift-off. (Yonhap)