Battisti has been in a Brazilian jail fighting extradition for the past four years  [Reuters]

Brazil's Supreme Court has rejected the extradition to Italy of a former far-left militant and ordered his immediate release in a case that has heightened tensions with Rome.

Italy immediately denounced the ruling on Wednesday with Giorgia Meloni, the youth minister saying that the latest move to free Cesare Battisti, who has been sentenced to life for the murders of four persons in the 1970s, was "a slap in the face for Italian institutions, an act unworthy of a cvilized and democratic nation."

"The decision by the Brazilian supreme judges not to authorize the extradition of a criminal like Battisti, just like that of then-president Lula, represents the umpteenth humiliation for the families of his victims." Meloni said.

The nine member court ruled by a 6-3 majority that the decision taken by Luiz Inacio Lula da Silva, the former president, to deny the Italian extradition request and authorise Battisti to remain in Brazil complied with a bilateral treaty.

The judges also said that Battisti, 56, who has been in jail fighting extradition for the past four years, should be immediately freed.

Battisti, a member of the radical Armed Proletarians for Communism (PAC) group, became an international fugitive after escaping from an Italian jail in 1981 and spent decades evading justice, living in Mexico, France and Brazil.

He was convicted in his absence by an Italian court in 1993 for the murders of four people in the 1970s, charges he has denied, and sentenced to life imprisonment.

Political refugee

Brazil granted him political refugee status in January 2009, in a move that effectively halted extradition proceedings.

But eight months later, the Supreme Court nullified that decision and said it favoured extraditing him to Italy, at the same time ruling that Lula should be the final arbiter.

In late December 2010, Lula, in his last moments in office, enraged Silvio Berlusconi, the Italian Prime Minister, by denying the extradition.

The Italian government appealed, and Brazil's nine Supreme Court justices discussed the legality of Lula's decision on Wednesday.

The court also ruled by 6-3 that Italy did not have legal standing to challenge Lula's decision.

"At stake here is national sovereignty. It is as simple as that," Judge Luiz Fux said, to justify his vote against Battisti's extradition and in favour of his release.

Battisti has insisted that he is innocent.

One of his lawyers, Renata Saraiva, told the daily O Globo he was "very anxious" as he awaited the ruling, taking anti-depressant medication to handle the stress.

It remained unclear if the current president, Lula's successor Dilma Rousseff, will still have the ultimate say in the case.