"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 the second 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.
The South Korean military is currently searching for rocket debris and has stepped up military alertness.
North Korea had indicated technical problems with the rocket and recently extended its launch window to Dec. 29.
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)