"As a member of the Swiss Olympic mission he gravely discriminated, insulted and violated the dignity of the South Korean football team and the South Korean people," Swiss team chief Gian Gilli told reporters.
The 23-year-old is the second athlete to be expelled by their own team over a racist Twitter comment at the first Games where social media are an integral part of the athletes' daily lives.
Greek triple jumper Paraskevi Papachristou was thrown out of her nation's team last week, two days before the Games started for a racist comment regarding African immigrants in Greece.
In his message, with some syllables jumbled, for which he was expelled, Morganella said on Monday morning: "I punch you, South Koreans, go burn..." The rest of the message was considered sufficiently offensive by the Swiss team for Morganella to be sent home.
Gilli, who only read out a statement in German and did not take any questions, said Morganella's comments were in direct violation of the International Olympic Committee's and the Swiss team's ethics codes.
He said Morganella, who has already left London, had been "provoked" on Twitter but his response was unacceptable.
"As a consequence of this behaviour Michel Morganella, having conferred with the Swiss Football Association, is immediately stripped of his Olympic accreditation and all future participation in the Olympic tournament.
"The Swiss team will now focus entirely on the next match. I wish the team inner peace and serenity," Gilli said.
The player himself said he accepted the sanction and apologised.
"I made a huge mistake after the disappointing result. I wish to apologise to the people in South Korea and their team, but also to the Swiss delegation and Swiss football in general. I obviously accept the consequences for my actions."
The Swiss, third in Group B, play Mexico in their next game on August 1 which is also Switzerland's national day.
Gilli said he had also - unsuccessfully - tried to contact the Korean team.
"We would like to apologise, especially to the South Korea National Olympic Committee and the South Korea Football Association for the behavior of the player," he said.
"We hope that he will draw the necessary lessons for his still young football career," he said of Morganella.
The London Games are the first Olympics where social media are so widespread. The IOC has urged athletes to tweet but to always respect the Games ethics code which all teams and athletes have signed.
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