The protest was part of worldwide naked bike riding events on Saturday across Europe, North America and South America.

"We feel naked when up against traffic because people don't see the bicycle as just another means of transport," said Madrid cyclist Ramon Linaza, wearing only a cycle helmet and shoes.

Towing cardboard cars with gaping jaws, protesters said the rapid rise of automobile ownership in Spain was turning city streets into ever more hostile and dangerous cycling territory.

Organisers said the bicycle was a healthy and efficient form of urban transport that is largely ignored by Spanish drivers and city planners.

Central Madrid has few bike paths and cyclists are a rarity on its streets. Barcelona has the most bike paths of any Spanish city, according to cycling activists.