Japan on Thursday successfully launched a replacement spy satellite, its aerospace agency said, as an existing device comes to the end of its working life.

Tokyo put spy satellites into operation in the 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 launched the H-2A rocket from Tanegashima Space Center in southwestern Japan, the agency said.

The launch at 10:21 am (0121 GMT) went smoothly, a JAXA spokeswoman said, noting "the satellite separated and entered orbit as scheduled."

Five Japanese intelligence satellites are currently in orbit -- two optical satellites and three radar satellites, including a backup radar satellite launched last month.

The new satellite will succeed one of the two optical satellites that was launched in 2009, a Cabinet Office official said.