Eight Panama workers of Canadian miner First Quantum were injured when protesters hurled rocks at a bus transporting them, a union leader said on Sunday, as tensions flared at the company's lucrative mine in the Central American country.

The unrest comes during protests in Panama sparked by the Oct. 20 approval of a contract for the company to operate a key copper mine that represents about 5% of the country's GDP and some 1% of global copper output. Protesters have previously demonstrated over the mine's environmental and economic impacts.

Workers were injured as protesters smashed the bus' glass windows when they were leaving the mine located in Panama's Cocle province, said union leader Michael Camacho. The company's local unit Minera Panama said in a statement that one worker and some contractors were attacked in a violent incident.

"The affected worker is in stable condition and currently receiving medical attention and emotional support," the company statement said.

Reuters was not immediately able to contact the protesters.

Panama's police said in a social media post that a bus of a private company had suffered damages after incidents with protesters near the mine, without naming the company.

First Quantum was forced to shut down commercial production earlier this week, following blockades by protesters at a key port that prevented the miner from receiving shipments of essential supplies.

Panama's top court started deliberations to rule on several constitutional challenges to First Quantum's contract on Friday and is expected to issue a ruling in the coming days. REUTERS