The Champions League quarter-final between Inter Milan and city rivals AC Milan was abandoned after 73 minutes on Tuesday after Milan keeper Dida was struck by one of dozens of flares thrown down from the stands.
German referee Markus Merk took the players off the pitch at the San Siro stadium after Inter fans began hurling plastic bottles and then over 30 flares on to the penalty area below them after a header by Esteban Cambiasso was disallowed.
Dida received medical treatment to his shoulder while Inter players urged their fans to stop hurling objects on to the pitch.
The goal frame disappeared in clouds of smoke as flares continued to rain down and burn on the pitch.
The players came back on to the field after 25 minutes but Merk took them off again after just 30 seconds play and abandoned the game when more flares came down with no sign of intervention from the police.
Milan were leading 1-0 thanks to a first-half goal from Andriy Shevchenko, which had put them 3-0 up on aggregate after they won last week's first leg 2-0 at the San Siro stadium the two clubs share.
UEFA's website reported that "referee Merk will now submit his report to the UEFA Control and Disciplinary Body, who will deal with the case".
Milan coach Carlo Ancelotti said Dida had suffered "a burn and bruising" from the flare and reckoned the events had stained the reputation of football in Milan.
"I can't remember anything like this in all the derbies I've witnessed in these years," said Ancelotti.
"The actions of the fans don't just punish Inter but all of the city of Milan."
SECOND TIME
This is the second time this season that a Champions League match in Italy has been abandoned following crowd disorder.
In September AS Roma's game at home to Dynamo Kiev was halted after referee Anders Frisk was hit by a missile thrown from the crowd and the Serie A club were ordered to play two European home games behind closed doors.
"There were two or three hundred hooligans who were involved in throwing the flares," said Milan police chief Paolo Scarpi. "They have been caught on video camera -- they were the usual hotheads from the Inter sector," he added.
Scarpi said a large number of flares had been confiscated at the entrance to the stadium before the game -- but clearly dozens more had been smuggled through.
He said the police were "present and as always they did their job".
The incidents in Milan do northing to dispel fears of trouble when Juventus host Liverpool in the second leg of their quarter-final on Wednesday.
The match is the first to be played by Liverpool against Juventus in Turin since the Heysel Stadium disaster in 1985 when 39 Juventus fans died after being charged at by Liverpool fans.
Although Liverpool staged a public apology for the deaths at the first leg in Liverpool last week, a number of Juventus fans turned their backs on the gesture and the threat of trouble in the return leg has prompted the authorities to increase security in Turin on Wednesday.
