FIFA president Sepp Blatter promised tough action from world soccer's ruling body on Thursday after Turkey's World Cup playoff defeat by Switzerland finished in violence that left one player hospitalised.
"I can tell you this, not as a Swiss but as the president of FIFA, that we will act here and we will act tough," Blatter told a news conference on Thursday announcing an investigation into the incidents before and after Wednesday's game in Istanbul.
"In the past few days, fair play has been trampled under foot, not just on the pitch but also outside. That hurts."
The punishment after the inquiry could range from a warning to the suspension of any football association found at fault. The investigation must be finished by December 9, the day of the draw for the 2006 World Cup finals, Blatter said.
Switzerland defender Stephane Grichting needed hospital treatment after being kicked in the stomach in an apparent free-for-all after the game. He needed a catheter inserted and will be out for up to 10 days.
The Swiss, 2-0 up from the first leg, reached the World Cup finals in Germany next year on away goals despite Turkey winning Wednesday's second leg 4-2.
The visiting players left the pitch under a hail of objects thrown by the Turkish crowd. Players from both sides clashed as they ran off the field.
"This was an experience I could have done without," Swiss captain Johann Vogel told reporters at a news conference in Zurich. "I have never been scared on the pitch before."
Swiss coach Koebi Kuhn said security staff, there to protect the players, had joined in attacks on his team.
"Players, not just players, were beaten...they were thrown to the ground by security who should have been in charge of their safety," Kuhn said.
"I hope this will be sanctioned but the matter is done for me. I am preparing for the World Cup now. But it is unforgivable that such things should happen."
Swiss midfielder Johann Lonfat said the intimidation had gone beyond normal limits: "I was told: 'We're going to slit your throat'."
Blatter, who described himself as "hopping mad" added: "It [the inquiry] will show whether we will investigate against Switzerland, too.
"At the moment we're just questioning and we're questioning both sides because, of course, the Swiss want to justify themselves after what has happened."
Turkish Football Federation chairman Levent Bicakci criticised Blatter's comments.
"Our federation finds the FIFA president's statement really odd and we will do whatever we can to clarify this event and to make sure Switzerland gets the same penalty as Turkey," he said.
Turkey, surprise semi-finalists at the 2002 World Cup, had two fines for crowd disturbances plus two warnings during their World Cup qualifying campaign, FIFA officials said.
On arrival at Istanbul airport the Switzerland squad was kept waiting for two hours at passport control and baggage reclaim. Police struggled to hold back fans shouting abuse at the Swiss players and the team bus was pelted with eggs.
In contrast, on the Swiss side's return to Zurich, hundreds of fans clad in red showed an unusual outburst of emotions, sounding cow bells and waving Swiss flags.
On Tuesday Swiss foreign minister Micheline Calmy-Rey sent a letter of complaint to the Turkish government, calling the team's reception by Turkish fans "unacceptable behaviour".
The Turkish football federation has in turn protested that Swiss fans jeered their national anthem in the Bern first leg and Turkish players had been abused after Saturday's match.
"The incidents in Switzerland put a nation on edge...They exerted psychological pressure off the pitch," the Turkish Federation's Mosturoglu said.
Blatter said events in Bern would also be investigated.
On Wednesday television pictures showed Swiss player Benjamin Huggel kicking out at Turkey's assistant coach Mehmet Ozdilek as he left the pitch.
Kuhn said: "Of course that happened but I can assure you that Huggel is a good man. He was provoked, he was beaten, he was defending another player."
(Additional reporting by Daren Butler in Istanbul and Tim Heritage in Paris)