Rio de Janeiro: Brazilian oil workers and oil giant Petrobras are locked in a power struggle over the company's privatisation plans, with the union saying thousands of employees are on an indefinite strike.

The Unified Federation of Oil Workers said 21,000 employees in 13 states have joined the strike since it kicked off on February 1 - about 60 per cent of the company's workforce.

Petrobras, contacted did not confirm those numbers.

Oil workers march against layoffs at the state oil company Petrobras in Rio de Janeiro, Brazil, on Tuesday. Credit:AP

A few hundred people gathered on Tuesday afternoon, local time, outside the headquarters of state-controlled Petrobras in Rio de Janeiro, waving flags and protesting against recent layoffs in the state of Parana.