Brazil's scandal-plagued state oil giant Petrobras announced third-quarter losses of about $1 billion on Thursday, mainly due to the sharp devaluation of the Brazilian currency.

Petrobras, mired in a hugely damaging scandal involving bribes and high-level political payoffs, posted losses of 3.76 billion reais in the quarter, compared with a loss of 5.3 billion reais a year earlier.

The huge corruption case has cost Petrobras more than $2 billion and shaken Brazil's political establishment to the core.

The third-quarter loss was much steeper than analysts expected, underlining the grave uncertainty surrounding Petrobras.

Police have revealed that Brazil's major construction companies formed a cartel to divvy up Petrobras contracts -- overcharging it by one to three percent -- in exchange for bribes paid to executives at the company, politicians and political parties.

Brazil, the world's seventh-largest economy, is struggling with an economic recession, high inflation and rising unemployment.