UPDATE 2-Brazil's Petrobras fires manager after probe into share trades

(Adds information on internal probe, adds context)

By Gram Slattery, Marta Nogueira and Sabrina Valle

RIO DE JANEIRO, March 29 (Reuters) - Brazil's Petrobras has fired a high-ranking manager after determining he had traded company shares in the days leading up to the firm releasing its financial results, the company said on Monday.

Earlier on Monday, four sources familiar with the matter told Reuters that Claudio Costa, Petrobras' executive manager for human resources, sold shares during the company's "quiet period" before its results release in late February, which is a regulatory violation in Brazil.

The trades occurred shortly before Brazilian President Jair Bolsonaro announced he was firing Chief Executive Roberto Castello Branco in February, a development that sent Petrobras shares into a tailspin, said the people, who requested anonymity to discuss private matters.

"The executive manager for human resources was dismissed from the company today," said Petrobras, citing its statute that prohibits the trading of securities of companies linked to it in the 15 days before the release of financial statements.

Costa referred Reuters to the press office of Petroleo Brasileiro SA, as the company is formally known.

Three of the sources said the company had regarded the timing of the trades as noteworthy, but Petrobras has not determined whether or not laws pertaining to insider trading had been violated.

Castello Branco personally approved the dismissal, one of the sources said.

Petrobras said Pedro Brancante, the chief of staff to Castello Branco, will take Costa's place on an interim basis.

Castello Branco's sacking came after the company hiked domestic fuel prices more than 30% in less than two months, drawing the ire of Bolsonaro, whose constituents include truckers who frequently complain about diesel prices. The incident sent investors for the exits, with Brazil-listed preferred shares falling over 20% in one day.

Castello Branco is set to be officially replaced in mid-April by Joaquim Silva e Luna, a retired general who previously ran the Itaipu hydroelectric dam on the border of Paraguay and has no experience in the oil and gas sector. (Reporting by Gram Slattery, Sabrina Valle and Marta Nogueira; Additional reporting by Jamie McGeever in Brasilia Writing by Ana Mano; editing by Jonathan Oatis and Richard Pullin)