By Hyunsu Yim and Nobuhiro Kubo

SEOUL/TOKYO (Reuters) -North Korea has notified Japan of a plan to launch a satellite between May 31 and June 11, a Japanese coast guard official said on Monday.

Analysts say the military satellite is part of nuclear-armed North Korea's efforts to advance surveillance technology, including drones, to improve its ability to strike targets in the event of a conflict.

North Korea has also undertaken a series of missile and weapons tests in recent months, including a new, solid-fuel intercontinental ballistic missile (ICBM).

North Korea informed the Japanese coast guard of the planned launch, the coast guard official told Reuters, confirming earlier reports by public broadcaster NHK and other Japanese media.

The Japanese prime minister's office urged North Korea to refrain from the launch and said it would work closely with allies.

"We strongly urge North Korea to refrain from launching," the prime minister's office said on Twitter, adding it would cooperate "with relevant countries such as the U.S. and South Korea".

The Japanese government would do all it could to collect and analyse information from the launch, it said.

North Korea had said it had completed work on its first spy satellite. North Korean leader Kim Jong Un in May inspected a military satellite facility, North Korean state media KCNA reported.

The KCNA report said Kim had approved next steps of the non-permanent satellite-launching preparatory committee.

North Korean media previously criticised plans by South Korea, the United States and Japan to share real-time data on Pyongyang's missile launches, describing the three as discussing "sinister measures" for tightening military cooperation.

(Reporting by Hyunsu Yim in Seoul and Nobuhiro Kubo in Tokyo; additional reporting by Ju-min Park in Seoul and David Dolan in Tokyo; Editing by Diane Craft and Howard Goller)