Activists say the horse was "hot and tired", driver claims the animal "slipped".

A carriage horse collapsed in front of tourists at Rome's Trevi Fountain on Saturday night, amid claims by two American activists that the animal fell to the ground due to being "exhausted from the heat".

However the driver of the horse-drawn carriage, or botticella, alleges the animal "slipped" after sticking its neck out to get some food, either from somebody or off the ground, reports newspaper La Repubblica.

Angelo Sed, head of carriage drivers' association Nuova Associazione Vetturini Romani, told La Repubblica that the horse is "fine and healthy" and denied that the heat was to blame for the incident.

"We started at 18.00, as per the regulations" - Sed stated - "it's impossible that it happened because of the heat, late at night."

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The American activists, who were moved away from the scene by police, claimed the animal "could not take it anymore" after hours of working in the heat, La Repubblica reports.

Under the city's updated rules, in force until 15 September, botticelle are prohibited from operating between 11.00 and 18.00 on the hottest days of the summer, when the heat warning is at risk level 2 and 3.

It is far from the first time that a horse has collapsed in Rome while pulling a botticella carriage, a tradition the city has tried (and failed) several times to move off the streets and into parks.

Any attempt to curtail the botticelle - which animal rights activists want abolished - has been met with fierce opposition from the carriage drivers who have succeeded in blocking measures through the courts.

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Over the years there have been numerous clashes between carriage drivers and animal rights' activists who describe the city's streets as a "cruel" working environment for the horses, several of whom have collapsed and died under the strain of the summer heat.

In 2008 an 18-year-old horse died on the street while at work near the Colosseum.

In 2012 an exhausted horse collapsed in Piazza di Spagna, under the strain of carrying six tourists in 40 degree heat. The driver attempted to beat the animal back to work and only ceased following the intervention of police.

In 2014 a horse collapsed on Via del Corso, near Italy's parliament, after the driver claimed it slipped in oil, with the same thing happening near the Spanish Steps in 2019.

Photo La Repubblica