BUENOS AIRES (Reuters) - An Argentine prosecutor's mysterious death days after he made criminal charges against President Cristina Fernandez is part of an attempt to unseat her and bring neoliberals back to power, a senior government official said on Monday.

The comments by Gustavo Lopez, an undersecretary in the presidency, follow the death of Alberto Nisman on Jan. 18 after he accused the president of derailing his investigation into a 1994 bombing of a Jewish community center.

Nisman's accusations and his death have rocked Argentina and sparked a myriad of conspiracy theories.

Some Argentines pin his death on the government, while President Fernandez has suggested it was part of a murky plot by rogue intelligence agents to smear her name.

Either way, it has triggered one of the biggest political crises of Fernandez's seven-year rule and may bolster the opposition's chances of a win in October's presidential vote.

Lopez wrote in a statement that this was the exact aim.

"We are facing an attempted coup d'├ętat, that aims to get rid of the president, to end this political project that has been governing since 2003 and to restore the neoliberal conservative forces that governed for decades to reap their own benefits," wrote Lopez, who has in the past spoken to the press about the Nisman case and other issues facing the government.

Lopez said the government of Fernandez and her late husband and predecessor Nestor Kirchner had confronted many sinister forces during their years in power such as the "international economic interests that live from usury, weapons trafficking and money laundering".

"Now they have come to get their revenge. They cannot stand the Front for Victory (ruling coalition) winning another presidential period and if they need to provoke a political death to achieve this, they will do it," Lopez wrote.

State prosecutor Nisman who was investigating the 1994 attack that killed 85 was found dead in his flat with a gunshot wound to the head. It remains unclear whether he committed suicide or was murdered.

Nisman had accused Fernandez of attempting to cover up for the Iranian suspects in the bombing in order to normalize relations with Tehran and access Iranian oil. Iran has denied any involvement in the attack.

Fernandez has lambasted Nisman's accusations as ridiculous, while the judge in charge of the bombing case has said his evidence was "flawed".

"Nisman's weak charges, which would not pass the exam of the first year of university study, were not enough to maintain the scandal," Lopez wrote. "Their policy is to sustain the scandal, hence the death."