North Korea said its attempt to launch a military reconnaissance satellite failed Wednesday when the second stage of the rocket failed, according to the state-run Korean Central News Agency (KCNA).

"The new satellite vehicle rocket, Chollima-1, crashed into the West Sea ​​as it lost propulsion due to an abnormal startup of the engine on the 2nd stage after the 1st stage was separated during normal flight," KCNA said.

Earlier, South Korea's military said Pyongyang fired a "space projectile," triggering emergency alerts in Seoul and Japan, weeks after North Korean leader Kim Jong Un ordered officials to prepare to launch the country's first military reconnaissance satellite.

South Korea's Joint Chiefs of Staff said the launch occurred around 6:29 a.m. Two minutes later, an air raid siren sounded in Seoul, and a minute after that a text message was sent urging residents to "prepare to evacuate and allow children and the elderly evacuate first."

Another message followed at 6:41 a.m. to say the warnings were "sent in error."

Japan's Defense Ministry had warned on Monday it would destroy any North Korean missile that entered its territory after Pyongyang notified the country of plans to launch a "satellite" between May 31 and June 11.

Wednesday's launch triggered alarms in Japan, where alerts issued for the Okinawa prefecture were later recalled after authorities there determined there was no threat to Japanese territory.

South Korea's Joint Chiefs of Staff said the projectile was launched from Tongchang-ri, Pyongan province towards the south, and was detected flying over the west of Baengnyeong Island in the Yellow Sea.

A separate warning was issued for Baengnyeong Island that was lifted just after 8 a.m, according to South Korea's Ministry of Interior and Safety, which said the projectile was launched over the West Sea.

This is a breaking story. More to come.