Brazil's state oil company Petrobras warned on Thursday that court injunctions blocking its price increases for natural gas undermine "legal security" and threaten government efforts to open up the domestic market and attract private investment.

Petroleo Brasileiro SA, as the company is formally known, said in a securities filing that it had been officially notified of preliminary orders issued by a Rio de Janeiro court blocking its price hikes for clients in the state.

The injunctions from the Rio court affect contracts between Petrobras and state gas distributors CEG and CEG RIO.

State courts in Ceara, Sergipe and Alagoas issued similar orders blocking natural gas price hikes in contracts with gas distributors in those states, the filing said. The court orders were first announced on Tuesday.

"These decisions undermine the legal security of the business environment," Petrobras said of the court orders.

"These interfere with free market practices, putting at risk the implementation of the opening up of the natural gas market in Brazil and the attraction of investments into the country."

Petrobras has said it would try to overturn the injunctions, which block proposed price increases from taking effect in January.

Petrobras said the price hikes are justified amid high global demand for natural gas and supply limitations that caused international prices to rise by about 500% in 2021.