TOKYO (AFP) - Japan on Sunday successfully launched a back-up spy satellite, its aerospace agency said, after cancelling an earlier lift-off due to bad weather.

Tokyo put spy satellites into operation in the early 2000s after its erratic neighbour North Korea fired a mid-range ballistic missile over the Japanese mainland and into the western Pacific in 1998.

The Japan Aerospace Exploration Agency (JAXA) and Mitsubishi Heavy Industries delayed Thursday's planned launch of the H-2A rocket from Tanegashima Space Center in southwestern Japan, due to the possibility of lightning during lift-off.

The launch at 10.21am on Sunday was successful, JAXA and Mitsubishi Heavy said, adding: "We confirmed the rocket launched normally."

Four Japanese intelligence satellites are currently in orbit - two optical satellites and two radar satellites. The backup satellite will supplement the two radar satellites, a government official said earlier.