Greek triple jumper Voula Papachristou has been expelled from her country's Olympic team over comments she posted on Twitter which were deemed racist.

Papachristou was due to compete in the London 2012 Games, which officially start this Friday.

But the Hellenic Olympic Committee said her posts mocking African immigrants and expressing support for a far-right party went against the Olympic spirit.

Papachristou has apologised for the "unfortunate and tasteless joke".

As well as the comment on Monday referring to the West Nile virus and Africans living in Greece, Papachristou also reposted a tweet by Ilias Kasidiaris, a politician with the far-right Golden Dawn party, criticising Prime Minister Antonis Samaras's stance on immigration.

Her remarks had sparked calls from the public and within the Greek government for her to be thrown out of the team.

The head of the Greek committee, Isidoros Kouvelos, said the 23-year-old had "showed no respect for the basic Olympian value".

"She made a mistake and in life we pay for our mistakes," he told SKAI TV.

The spirit of the games is about the power of sport over politics, where perseverance and hard work are paid off with medals; where ordinary people can become national heroes.

This ideology has been expanded over the years. In the words of the London2012 official education programme, Get Set: "The Olympic and Paralympic Games are about much more than sporting excellence."

In a statement on her Facebook page and Twitter, Papachristou said she was "very sorry and ashamed for the negative responses I triggered, since I never wanted to offend anyone, or to encroach human rights".

She apologised to her friends, family, fellow athletes and the national team, but said it would not have been possible for her to compete if she did not support the values of the Games.

"Therefore, I could never believe in discrimination between human beings and races."

The committee said she had been "placed outside the Olympic team for statements contrary to the values and ideas of the Olympic movement".

The BBC's Mark Lowen in Athens says Greece is experiencing a sharp rise in racism, with the popularity of right-wing parties like Golden Dawn soaring.

The government has come under pressure to crack down on racism in all domains, including sport, says our correspondent.