SAO PAULO -- A wave of alleged hate messages posted on Twitter immediately after Brazil's presidential elections must be investigated, a federal prosecutor said Thursday.

Janice Ascari said she has asked that law intern Mayara Petruso of Sao Paulo and others be investigated for allegedly using Twitter to incite prejudice and discrimination against people from Brazil's impoverished northeast.

Ascari said that Petruso had posted messages asking people to kill northeastern Brazilians in reprisal for Dilma Rousseff's victory in Sunday's presidential election.

Rousseff enjoys wide support in the northeast and won a majority of the votes there.

While no killings are known to have taken place because of the messages, the postings "constitute a form of hate crime because they foster discrimination and prejudice and call for the killing of a specific group of people," Ascari said.

Petruso could not be located for comment and it was not immediately known if she had hired an attorney.

Law firm Peixoto e Cury Advogados said in a statement that Petruso was one of its interns but that she was not working for the company at the time she allegedly posted the messages.

Ascari said that Petruso's messages set off a wave of similar Twitter postings that she wants investigated as well.

Residents of Brazil's wealthier and more developed south often look down on people from the poorer northeast, many of whom migrate to the south in search of better jobs and living conditions.

Henrique Mariano, president of the Brazilian Bar Association's chapter in the northeastern state of Pernambuco, said he asked prosecutors in Sao Paulo to locate Petruso and begin criminal proceedings against her for "for inciting people to commit murder."

Luiz Flavio Borges D'Urso who heads the Sao Paulo chapter of the Brazilian Bar Association said "we cannot tolerate xenophobic, racist and prejudicial attitudes, especially coming from a law student who instead of seeking social peace ... incites others to hate."