TOKYO - A BALD, naked man who said he was Spanish went swimming in the moat of Japan's Imperial Palace on Tuesday, climbing the palace wall, throwing rocks and splashing water at police before being taken into custody.

Television footage showed the tall man getting out of the water at one point, chasing police with a rock and a plastic construction site pole.

He then dove back into the murky water and swam across to the other side of the moat, climbing up the 8-metre stone wall of the palace.

He was caught by two policemen, after a chase media said lasted for an hour and a half.

'I've never heard of anyone doing such a thing,' an unidentified man at the scene told TV Tokyo. 'He must be a bit crazy.'

Television showed passers-by gathering around the moat and watching the chase, giggling and taking photos on mobile phones.

Police said it was unclear what his motives were, although media said he had dropped a bag in the water.

'We are checking on his mental condition now,' a police spokesman said.

The palace, in the heart of Tokyo and home to Japan's emperor and empress, is surrounded by 12 moats running 7 km in all.

Tourists can walk freely around the periphery of the palace and go inside on a tour, but in general are not allowed to step within the premises of the 115 hectare (284 acre) palace grounds. -- REUTERS