Brazilian prosecutors on Friday opened a probe into allegations that President Jair Bolsonaro sat on evidence of corruption in a Covid vaccine deal.

The move by the attorney general's office, headed by Bolsonaro allies compelled to act by the nation's high court, added to growing pressure on the far-right leader but seemed unlikely to result in the president's removal from office any time soon.

Even if investigators finds evidence of wrongdoing, the Supreme Court can only open a case against Bolsonaro with approval of congress, where he holds sway.

The attorney general's office said in a statement Friday it had informed the Federal Supreme Court "of the opening of an investigation into events reported" by three senators who have formally asked for an investigation of the president for malfeasance.

The office was compelled to do so after the court turned down its initial request to throw out the senators' bid, which stems from accusations made before a senate commission looking into the government's handling of the coronavirus pandemic.

The outbreak has claimed more than 520,000 lives in Brazil -- the second-highest death toll after the United States.

The commission was told last week that a deal to purchase the Indian-made Covaxin vaccine was a front to embezzle millions of dollars, that a Bolsonaro ally masterminded the plan -- and that the president knew all about it, but did nothing.

A health ministry official testified that his superiors had exerted "atypical, excessive" pressure on him to approve payment for the deal, which he suspected was over-billed.

The official and his brother, a congressman close to Bolsonaro, said they took the matter to the president, but he took no action.

This is the evidence which prompted three senators to ask the Supreme Court to investigate Bolsonaro.

Brazilian President Jair Bolsonaro is accused of knowing about but failing to report alleged corruption in the purchase of a coronavirus vaccine
Brazilian President Jair Bolsonaro is accused of knowing about but failing to report alleged corruption in the purchase of a coronavirus vaccine AFP / EVARISTO SA

Attorney General Augusto Aras, whose job it is to decide whether to bring charges or not, is an ally of the president.

His deputy, Humberto Jacques de Medeiros, had asked the Supreme Court to reject the senators' request, but this in turn was rejected by judge Rosa Weber, who said the attorney general's office could not be "a spectator of the actions of the powers of the republic."

Madeiros was thus compelled to file a request to the Supreme Court for authorization to seek information in the case "and the eventual transfer of evidence" collected by other judicial and legislative bodies.

If prosecutors find any evidence, they would approach the Supreme Court to open a case against Bolsonaro.

But this seemed very unlikely, with Bolsonaro enjoying majority support from a loose alliance of conservative parties that has so far blocked more than 100 impeachment bids brought by opponents.

"The acceptance to investigate (the senators' complaint) is a defeat for the president, but I do not see any element that guarantees a guilty finding," political analyst Creomar de Souza, of the consulting firm Dharma, told AFP.

The polarizing president has faced growing outrage over his handling of the epidemic, which he is accused of criminally mismanaging.

Bolsonaro -- who himself contracted Covid-19 -- minimized the virus as a "little flu," fought lockdowns, questioned face masks and rejected various offers of vaccines, while pushing unproven drugs such as chloroquine and urging Brazilians to get back to work.

On Wednesday, opposition lawmakers launched a fresh bid to impeach him amid yet more allegations of vaccine purchase corruption.

A document signed by dozens of left-wing political parties, trade unions and civic organizations, as well as a few former allies, was submitted to the chamber of deputies, listing more than 20 accusations against the president, including "negligence."

Protests have been organized for Saturday to call for Bolsonaro's resignation.