Japan plans to launch a spy satellite in September aimed at helping it keep an eye on neighbouring North Korea following Pyongyang's launch of a series of missiles earlier this month.

The information-gathering satellite will be Japan's third, after the successful launch of a pair of satellites in March 2003. Two other satellites were lost when a rocket failed in November that year.

The optical satellite will be launched from Tanegashima in southern Japan on September 10, an official at Japan's Cabinet Satellite Intelligence Centre said on Thursday.

The satellite will be able to differentiate objects a metre or more in diameter, though US military satellites offer far better levels of resolution.

A ban on defence use of space dating from the 1960s has hampered Japan's ability to develop high-tech hardware.

Japan planned its spy satellite programme following North Korea's 1998 launch of a ballistic missile that flew over Japan and landed in the Pacific Ocean.

On July 5, Pyongyang launched another volley of missiles, sparking unease across the region.