A 21-year-old man has been arrested after attacking another man, 65, who was forced to defend himself with a bar stool, according to media reports in Italy.
He was punched and hit his head as he fell.
He is in an induced coma with his condition being described as "very serious".
A Foreign Office spokeswoman said: “We can confirm the arrest of a British national in Italy on 21 March.
The Italian newspaper La Repubblica said that seven fans began fighting outside a bar before England's 8-0 win in San Marino, a venue over 70 miles away from the match.