Greece's triple jumper Paraskevi Papachristou has been barred from the Olympics, due to begin on Friday in London, for composing a "racist" tweet, the country’s Olympic committee said.
Papachristou tweeted that "With so many Africans in Greece... the West Nile mosquitoes will at least eat homemade food!!!"
"She showed no respect for a basic Olympic value and unfortunately she is out," Isidoros Kouvelos, who heads Greece's mission to the games, told SKAI TV.
"She made a mistake and in life we pay for our mistakes."
Papachristou's tweet appeared to divide opinions in Greece, which has long struggled with an influx of illegal immigrants from Africa and Asia and has seen a sharp rise in anti-immigrant sentiment amid its economic crisis.
Those who pushed for her expulsion included the co-ruling Democratic Left party.
"She can make as many vile 'jokes' as she likes on social networking sites when she watches the Olympic Games on TV," the party said in a statement.
But fans rushed to her defence, flooding her Facebook page with messages of support.
The 23-year-old athlete, who was scheduled to leave for her first Olympics next week, later apologised for what she said was "an unfortunate and tasteless joke".
"I am very sorry and ashamed for the negative responses I triggered, since I never wanted to offend anyone," Papachristou, a blonde-haired athlete who sports a navel piercing, wrote on her Facebook page in Greek and English.
"My dream is connected to the Olympic Games and I could not possibly participate if I did not respect their values."
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The Athens-born athlete was a long shot for a medal with a season's best of 14.58 metres, almost half a metre behind the world leaders.
Papachristou's coach criticised the decision to kick her out of the games, saying it was too harsh a punishment for someone who had already apologised.
"It's too much, the penalty should not have been so strict," George Pomaski told the Reuters news agency.
"This is a big disappointment not only for her but for her family and for myself and anyone involved in the Greek team."
One man has died in a small outbreak of the West Nile virus in Athens this month and at least five other cases have been reported, Greece's disease control and prevention body said.
Papachristou's withdrawal is a blow for Greece, which was hoping its Olympics team would be a source of pride for an austerity-hit nation deeply hurting from a debt crisis.
Greece is sending 105 competitors in 16 sports to the London Olympics.