A space panel headed by Prime Minister Taro Aso agreed to the plan as part of a new space policy document, a year after Japan dropped a decades-old ban on military use of space.

The launch of what Pyongyang said was a satellite-bearing rocket in April this year, followed by a nuclear test and a series of short-range missile launches last week, added urgency to complaints Japan's satellite intelligence-gathering system needed upgrading.

Japan launched four spy satellites following North Korea's 1998 launch of a long-range missile that flew over Japan.

The space policy document said efforts would be made to increase the number of times photographs were taken of areas of concern, improve image quality and speed up the provision of information. The research will include efforts to develop an early warning sensor, the document said.

Japan's physical proximity to North Korea as well as the history of antagonism between the two nations has made Tokyo nervous about becoming a target of a missile launch, spurring it to build up a missile defence system in cooperation with the United States.

South Korea's Yonhap news agency said on Tuesday the North was preparing a mid-range missile launch, which follows reports that a long-range missile could be fired in weeks.

Last year Japan passed a law allowing the use of space for defensive military purposes. The exclusion of the military from space development had long been blamed for Japan's tendency to lag in the space industry. -- REUTERS