TOKYO - A drone marked with a radioactive sign landed on the rooftop of Japanese Prime Minister Shinzo Abe's office on Wednesday and later tested positive for small amounts of radiation, media reported.
The drone was carrying a small camera, a water bottle and a flare.
Kyodo news, citing police sources, said a "small quantity" of radiation was measured on the drone and that police were investigating.
Abe was in Indonesia on Wednesday attending an Asia-Africa summit. An official at the prime minister's office declined to comment.
It was not immediately clear who sent the drone or why. But a Japanese court rejected a bid by residents to stall the restart of a nuclear power plant in southwestern Japan on Wednesday, discarding worries about the safety of nuclear power in the wake of the 2011 Fukushima radiation disaster.
Televised aerial footage from the scene showed the drone with propellers covered under cardboard and later a blue tarp. Dozens of police officers were seen carrying it away.
Japanese broadcaster NHK said an official at the premier's office found the drone and that the device was around 50 cm (20 ins) in diameter. No-one was injured.