The bar was wrecked in the attack, and this morning there was no response from anyone working there. The bar is situated in one of the most visited squares in the centre of Rome.
Police in Rome say seven men were injured. Five were British, one Californian and one Bangladeshi.
Italian website Corriere Della Sera reports the British casualties are all men - aged between 20 and 60. It shows images of the damage done to the pub following the attack.
- One casualty was taken to Rome's San Camillo Hospital
- Three were taken to the Holy Spirit Hospital
- Three others being treated at Fatebenefratelli
The Italian newspaper La Repubblica has compared the scenes to "urban warfare". The violence is believed to have taken place at the Drunken Ship pub - images on La Repubblica's website appear to reveal the damage.
The Lazio fans were reportedly armed with knives, baseball bats, belts and knuckle dusters and they went on to "destroy" the venue. One witness told the paper: "We feared the worst."
A Tottenham fan is in a serious condition following a fight with masked assailants in Rome ahead of tonight's Europa League match against Serie A side Lazio, police have announced.
He suffered an injury to his artery in the incident, which took place in the early hours of this morning and left nine other Spurs supporters injured.
The group - which included nine British and one American - was outside a pub near the city centre when they were attacked.
A number of Italians involved in the fight were detained, a police spokesman added.