Ciatti died from his injuries soon after being taken to a nearby hospital, according to reports in several Italian dailies.
The attack was captured on CCTV and has shocked many viewers for the sheer violence with which the three Chechen men punched and kicked Ciatti in the head.
The three men, aged 20, 24 and 26, according to La Stampa, fled on foot. Local police arrested them soon after on the seafront.
Two of the three have since been released. Spanish police say only one man was "materially responsible," according to La Stampa.
Ciatti's father, having seen the savage CCTV footage, told La Stampa his son had "been killed like a dog."
In the video, Ciatti and his friend are kicked in the head by the three men while everybody else in the club stands watching in a semi-circle.
The quiet seaside town of Lloret de Mar has been left shocked by the brutal nature of the attack. A minute's silence will be observed for the victim today.
At the market where Ciatti worked in Florence, stalls have remained closed out of respect.
The club where the incident occurred has been closed down. Security were only on duty outside the club on the night Ciatti was killed, according to several reports in Italian dailies.