RIO DE JANEIRO (Reuters) - Brazil's largest fixed line carrier Oi SA <OIBR4.SA>, which is currently in bankruptcy protection, said on Monday that Chief Financial Officer Flavio Nicolay Guimarães resigned, without giving a reason for his departure.

Guimarães will be replaced by Ricardo Malavazi Martins, Oi said in a securities filing. As part of the move, Martins stepped down from his position on the board of Oi, the company said.

Martins previously worked at Brazilian bank Bradesco <BBDC4.SA> between 1990 and 2003 and as CFO for Petros, the pension fund for state-run oil company Petrobras <PETR4.SA>, for six years.

(Reporting by Stephen Eisenhammer; Editing by Cynthia Osterman)