Seoul: A military spy satellite launched by North Korea earlier in the day crashed into the Yellow Sea owing to an engine problem and it plans to carry out its second launch "as soon as possible," reported Yonhap News Agency.

According to Korea Central News Agency (KCNA), North Korea launched "Malligyong-1," the military reconnaissance satellite mounted on a new-type rocket named "Chollima-1," at its rocket launching station on the west coast at 6:27 am (local time).

The carrier rocket fell in the Yellow Sea "after losing thrust due to the abnormal starting of the second-stage engine after the separation of the first stage during the normal flight," said KCNA in an English-language dispatch.

The failure was due to "the low reliability and stability of the new-type engine system and unstable character of the fuel used," read the KCNA report, citing a spokesperson of the state-run space development agency.

North Korea also said that it would thoroughly investigate the serious defects that emerged in the latest satellite launch and take necessary measures to overcome them, pledging to "conduct the second launch as soon as possible through various part tests."

Both South Korea and Japan issued emergency warnings advising the residents to take cover indoors if they were outside.

Japan termed North Korea's projectile a "possible ballistic missile," reported Kyodo News quoting the Japanese Defence Ministry.

According to the official Korean Central News Agency (KCNA), North Korean leader Kim Jong Un directed his country's space agency to finalise preparations for the launch of Pyongyang's first military reconnaissance satellite.

Pyongyang alerted the Japan Coast Guard of three maritime hazard zones where objects may fall beginning Wednesday, two to the west of the Korean Peninsula and one to the east of the Philippines. All of these areas are not within Japan's exclusive economic zone, according to Kyodo News.

Vice Chairman of the Central Military Commission of the Workers' Party of Korea, Ri Pyong Chol, on Monday, said, "The North's military reconnaissance satellite is indispensable to tracking, monitoring, discriminating, controlling and coping with in advance in real time the dangerous military acts of the US and its vassal forces."

Ri noted "the reckless military acts" by the US and South Korea, telling KCNA, "We steadily feel the need to expand reconnaissance and information means and improve various defensive and offensive weapons", according to Kyodo News.

Japanese PM Fumio Kishida, while emphasising that Japan considers the launching of a rocket carrying a satellite equivalent to a ballistic missile test on the basis of historical precedent, warned that following through on the plan would be in violation of the UN Security Council resolutions.

Sanctions have been imposed on North Korea for its weapons-related actions in accordance with United Nations resolutions.

Pyongyang, which launched missiles a record 37 times last year, has continued to launch ballistic missiles this year, raising suspicions that North Korea is planning its eighth nuclear test in the near future, Kyodo News reported.