"Madness in Genoa", was Monday's headline in sports daily Gazzetta dello Sport, while all newspapers carried articles on the "shame" of Genoa for letting their hardcore "ultras" fans dictate terms to the players.
"These things must end quickly, putting up with this causes too much damage to Italian football," said Paris Saint-Germain coach Carlo Ancelotti, formerly at Chelsea, AC Milan and Juventus.
The referee stopped play as smoke bombs and firecrackers were hurled onto the pitch by a small contingent of Genoa's fans, some of whom then climbed over the perspex barriers separating them from the field.
The supporters, some of them hooded, demanded the players remove their shirts after chanting they were not worthy of wearing them.
While Siena retired to their dressing room, most Genoa players handed their shirts to captain Marco Rossi although striker Giuseppe Sculli refused and tried to negotiate with the supporters.
Serie A announced the two-game ban on fans in a statement.
Genoa also face upheaval on the field after colourful owner Enrico Preziosi, supposedly banned from football for previous misdemeanours, said in a radio interview that he was sacking coach Alberto Malesani and replacing him with Luigi De Canio.
Malesani was only reappointed at the start of this month having been previously sacked in December.
Genoa, who had hoped to mount a challenge for the Europa League spots at least this term, are 17th in Serie A only one position and one point clear of Lecce in the relegation zone with five games left.
Former Queens Park Rangers boss De Canio has a tough baptism on Wednesday with Genoa travelling to champions Milan, who are desperate for the win after slipping three points behind Juventus in the race for the Serie A title.
Sunday's scenes were reminiscent of a European Championships qualifier between Italy and Serbia at the same stadium in 2010 when visiting fans rioted and caused the match to be abandoned.
"I thought I was dreaming," said former Milan and Italy midfielder Demetrio Albertini, now vice president of Italy's football federation. "You only have to compare us with abroad to see that we have trouble managing our fans and our stadiums."
MATCH-FIXING SCANDAL
The episode is the latest blow to Italian football, which is already reeling from a new match-fixing scandal currently centred on Serie B team Bari but which threatens to escalate as prosecutors continue their investigations.
La Stampa daily said Italian football was made a laughing stock by "the photo of a bemused Marco Rossi transformed from captain to laundry boy" as he handed over his team-mates' shirts to the fans.
Under the headline "The shame and the cowardice" La Repubblica said Italian stadiums were "places where the law cannot enter and where the strongest have the power to take away everyone's dignity".
While the shirt-removal incident in Genoa was unprecedented, Italian football is not new to episodes of "fan power" from its notorious but influential "ultra" supporters.
The 2004 Rome derby between AS Roma and Lazio was abandoned after fans invaded the pitch due to a rumour, which turned out to be false, that a supporter had been run over by a police vehicle. On that occasion Roma captain Francesco Totti famously negotiated with representatives of the team's "ultras".
Other problems with hooligans contributed to Italy failing in its bid to host Euro 2016 while the country's crumbling stadiums were also a factor.
The president of Italy's football league Maurizio Beretta called for th
