Argentina's president Cristina Fernández de Kirchner was boosted last week when a judge dismissed criminal allegations that she conspired to shield Iranian officials from responsibility over the 1994 bombing of a Jewish community centre in Buenos Aires.

The judge, Daniel Rafecas, said in his ruling that there was no evidence whatsoever that pointed to Mrs Kirchner.

Rebuking the criminal complaint filed against her by Alberto Nisman, a prosecutor, days before his eerie death in January of a bullet to the head, Mr Rafecas said some of the evidence gathered, "far from minimally supporting the prosecutor's claim, contradicts it categorically and conclusively".

His ruling can be appealed by the prosecutor who revived Mr Nisman's case after his death.

In an acutely politicised nation, some of Mrs Kirchner's opponents questioned Mr Rafecas's impartiality, but he said he had not been pressured by the government or others.

Taking up the offensive after the judge's decision, Mrs Kirchner launched a fierce defence of her role in the investigation into the bombing, which killed 85 people, at her annual state of the union address to Congress.

She said she had sought the truth throughout her political career, struck out at Israel and pointed to separate corruption charges that previously enveloped the case. The investigation into the bombing has been "a chessboard for national and international politics", Mrs Kirchner said.

Tens of thousands of her supporters gathered outside Congress in what was considered a response to a march last month to honour Mr Nisman and express anger at Argentina's political establishment. Mrs Kirchner said the march, organised by a group of prosecutors, amounted to a judicial coup.