Horses not allowed to work during extreme heat.

As temperatures in Rome reach the high 30s centigrade, animal rights' activists are reminding tourists that the capital's horse-drawn carriages are forbidden from operating during the hottest part of the day.

Between 1 June and 15 September the horse-drawn carriages, or botticelle as they are known in Rome, are prohibited from circulating between 13.00 and 17.00. The animals are permitted to work only after 18.00 and only if temperatures are below 35 degrees that day.

The rules are part of legislation passed by the city last year but which only came into effect in June. Animal rights' activists have advised the public to be vigilant in case the laws are broken and have invited people to report any violations to the police.

Under city law, Rome's 38 botticelle horses are not allowed to work for more than six hours a day and must be allowed to rest in the shade between tours, as well as receive sufficient water and rest.

Over the years there has been increasing opposition to the botticelle from environmentalists who say the conditions in which the horses work are cruel and dangerous.

Last October an 11-year-old horse drawing a carriage collapsed in the middle of Via del Corso, in front of tourists and shoppers. After lying for some time on the ground the horse returned to its feet, uninjured. The driver, backed by the president of Rome’s horse-drawn carriages, claimed the animal had slipped in a pool of oil.

Three summers ago an exhausted horse collapsed in Piazza di Spagna, under the strain of carrying six tourists in 40 degree heat. The incident made headlines after the driver attempted to beat the horse back to work and only stopped following the intervention of police. A month later there were violent scenes in the same square when animal rights activists and botticelle drivers clashed, resulting in three arrests.

At least two of Rome's botticelle horses have died on the streets while working – one in 2007, the other in 2008.