The British Embassy in Rome said the victim was travelling on a minibus when it lost its way near the Olympic Stadium and was ambushed by rival fans.

An embassy spokesman said the injured man managed to make his way into the stadium where he was treated for a bleeding leg.

Rome is due to host the final of Europe's elite club competition in May and, after a string of hooligan-related incidents over recent years, it remains to be seen if tonight's events will effect the city's position.

The incident happened shortly before tonight's dramatic last-16 second leg which saw Arsenal squeeze into the quarter-finals after a sudden-death penalty shoot-out win.

The embassy spokesman said: "This bus got a bit lost around the stadium and some Roma fans tried to get on the bus.

"One managed to get on to the bus and there was a fight.

"The driver managed to get away when the Roma fan was pushed out of the bus."

The victim was able to watch the match after receiving medical care, the spokesman said.

He added: "We don't know if it was a stabbing or glass from a smashed window."

An Arsenal spokeswoman said: "A male Arsenal fan was believed to be stabbed outside the stadium.

"Roma fans threw stones at a bus, smashing windows, and an individual allegedly entered the bus and stabbed a fan."

A Foreign Office spokesman said: "We are aware of the incident that happened in Italy and we are providing consular assistance."