Tourists and shoppers in central Rome looked on in astonishment at the weekend as horse-drawn carriage drivers traded blows with animal rights activists in the busy Piazza di Spagna.

Three people were arrested – reportedly including the president of a European animal rights group – and five were taken to hospital. The other two arrested were drivers of botticelle, the horse-drawn carriages that have become an increasingly anachronistic sight on the streets of the Italian capital.

Sticks and bottles were said to have been in used in the fight, which began after animal welfare activists protested over a lack of thermometers in come carriages.

Under a recently approved by-law, botticelle are not allowed to take on passengers if the temperature is above 40C (104F).

Two of the carriage drivers were fined as a result. The fight was broken up by officers of the semi-militarised Carabinieri police, as holidaymakers gazed at the nearby Spanish Steps or looked for bargains in the square's fashionable shops.

The number of licensed carriage drivers has fallen to just 42, but the profession is a growing source of embarrassment to the city. Last month, one of the horses collapsed in the Piazza di Spagna. In December 2008, another had to be put down near the Colosseum after being panicked by a passing lorry, falling and breaking a leg.