A 51-year-old Italian man is reported to have walked into St Peter's Square and set himself on fire with a cigarette lighter.
According to Italian news agency ASNA, CCTV camera footage has not shown that the man doused himself in any flammable liquid at the scene.
It appears more likely that he had doused himself in some form of fuel before he arrived. Gasoline has been suspected by many news sources, but no confirmation has been made.
He reportedly set light to himself using his clothes as the initial fuse.
The man is reportedly alive, and was initially taken to the Vatican's Santo Spirito clinic with severe burns on the upper part of his body before being transferred to a larger hospital later.
Immediately after the incident, Vatican police forces closed the area off.
A statement from the Vatican reports that a Jesuit priest rushed to the scene, where he attempted to extinguish the flames by smothering them with his jacket.
Two police officers arrived soon after, wielding a fire extinguisher that successfully doused the flames. All three parties have been taken to hospital to deal with burns to their hands.
The identity of the man is unknown, as is his motive. He was however carrying a piece of paper with what is believed to be his daughter's phone number written on it.