The Mexican government has fired the top electoral-crimes prosecutor for revealing an investigation that opponents say indicates possible corrupt financing for the ruling party.

The Attorney General's Office says prosecutor Santiago Nieto was fired for violating agency rules, but didn't specify which rules.

An official with the office said Nieto revealed information about an ongoing investigation. The official was not authorized to be quoted by name. Criminal investigations are not public in Mexico.

But opposition parties said Friday that Nieto was fired because he was investigating whether bribe money paid by Brazilian construction giant Odebrecht had made its way into the campaign coffers of the ruling Institutional Revolutionary Party, or PRI.

The National Action Party said it opposed the firing and would fight it in the Senate.