A huge explosion at a petrol station in a Rome suburb on Friday left 45 people hurt, two of them seriously, and rattled windows across the Italian capital.

The blast around 8.20am was preceded by a fire caused by a gas leak during refuelling, according to Rome Mayor Roberto Gualtieri.

Gualtieri visited the charred and smoking remains of the petrol and liquified natural gas (LNG) station and an adjacent sports centre in the Prenestino neighbourhood of eastern Rome.

The explosion sent a fireball and thick black smoke into the air, and was heard on the other side of Rome, shaking windows and causing some residents to worry that a bomb had gone off.

"The explosion was really powerful. I felt my skin burning," Michele Secu, a 23-year-old who worked at the now-destroyed sports centre, told AFP.

Before the explosion, emergency services were called to investigate the gas leak and had evacuated the immediate area, including a children's summer camp.

Twenty-one of the 45 injured were from the emergency services, including 12 police officers, Rome police told AFP.

Two men were hospitalised and life-threatening condition, one with burns on 55 percent of his body, local health authorities told the AGI news agency.

Fabio Balzani, head of the sports centre, said if the fire had occurred just a bit later it could have been disastrous.

Some 60 children had been expected at the summer camp and around 120 people booked to use the swimming pool, as relief from a heatwave that has baked the city for the past week.

"It would have been a massacre, a catastrophe," Balzani told AFP.

Andrea Quattrocchi, the local chief of the Carabinieri police force, also said the timely intervention of his team was crucial.

"They extracted a person alive from a burning car," who was taken to hospital, he told reporters.

Witnesses said an ambulance exploded in the fire.

Prime Minister Giorgia Meloni said she was following the situation, and offered her support for all those injured. (AFP)