Tokyo: A small drone was found on the roof of the Japanese prime minister's office on Wednesday, apparently having been flown there, local media said. Staff at the official residence -- known as "the Kantei" -- discovered the 50-centimetre craft on top of the five-storey structure in central Tokyo around mid-morning, major broadcasters reported.

Aerial footage showed dozens of police officers swarming over the roof and helipad of the modern, glass-facade building, with the drone covered by a blue tarpaulin.