Serie A football made a low-key return in Italy on Sunday with four matches played behind closed doors.
Fans are searched as security is stepped up at the San Siro
All football was suspended last week after the death of a policeman in crowd trouble in Sicily and many stadia are shut until they meet safety standards.
A minute's silence was observed at the start of all matches in memory of Filippo Raciti, who died on 2 February.
Reigning champions Inter Milan played in front of empty seats at Chievo's Bentegodi stadium, where they won 2-0.
Adriano and Hernan Crespo sealed the victory which extended Inter's Serie A winning record to 15 straight league matches.
Inter boss Roberto Mancini claimed the season should be stopped now if clubs continue to be forced to play behind closed doors.
Mancini admitted: "My words are clearly a provocation but to play without fans makes no sense.
"This is not football, we might as well quit right here and start again in September.
"We should do as they do in Formula One. When the conditions are no longer favourable, they stop and the one who is leading, wins," said the boss of the Serie A leaders.
The San Siro was only open to its 37,000 season-ticket holders but it made little difference as AC Milan defeated Livorno 2-1.
Ronaldo made his Milan debut, coming on as a substitute in the 63rd minute, but Gennaro Gattuso and Marek Jankulovski were the scorers.
The start of the Sicilian derby between Messina and Catania, which was also played behind closed doors, was delayed because of a waterlogged pitch.
It was at Catania's match with Palermo that Raciti was struck by a blunt object during rioting.
The Italian government is now drawing up strict new anti-hooliganism measures in response to the violence.