Political leaders in Athens and thousands of internet users have rounded on IMF chief Christine Lagarde for branding Greeks tax-dodgers.
Socialist leader Evangelos Venizelos accused Lagarde yesterday of trying to "humiliate" the debt-stricken country.
Greece is facing its second election in six weeks, a vote seen as crucial to the future of the euro zone.
Radical left-wing leader Alexis Tsipras, whose Syriza party is one of the two top contenders for the June 17 vote, insisted "Greek workers pay their taxes, which are unbearable".
Greek web users waged Facebook war against Lagarde, with the French managing director of the International Monetary Fund receiving more than 10,000 messages, many of them obscene, on her page on the online social network.
Their anger was sparked by comments Lagarde made in Britain's Guardian newspaper on Friday that Greeks must "help themselves collectively" by all paying taxes, saying she was more concerned about Africans in poverty than Greeks in the economic crisis.
Lagarde responded to the flood of angry online messages by responding on Facebook that she was "very sympathetic to the Greek people and the challenges they are facing."
"That's why the IMF is supporting Greece in its endeavour to overcome the current crisis," she added on the social networking site.
The comments by the French IMF head came as parties squared off for the election that could determine whether Greece continues to receive EU-IMF funds as part of a multi-billion euro bailout package and stays in the euro zone.
Tsipras seized on her comments to assert his stance as a defender against economic cuts, which drove many Greeks to vote for him in an inconclusive election on May 6, putting him second ahead of Venizelos's Pasok party.
In France, whose Socialist President Francois Hollande has defended Greece's place in the euro zone and pushed for a more growth-oriented strategy in the crisis, government spokeswoman Najat Vallaud-Belkacem described Lagarde's comments as "rather simplistic and stereotypical".
Venizelos welcomed Lagarde's Facebook message, after telling an election rally: "Nobody can humiliate the Greek people during the crisis."
The country will head to the polls for a second time in six weeks on June 17 since political parties failed to form a coalition after the May 6 election.
Former prime minister Lucas Papademos has warned that Greece may run out of money by the end of June if international bail-out funds are cut off following the election, To Vima newspaper reported yesterday.
