Canadian miner First Quantum Minerals on Tuesday responded to opposition to Law 406, which approves the refreshed mining concession contract for the company's Cobre Panama mine.

The company said "unconstitutionality challenges" have been brought against Law 406, and currently two of them have been admitted to be heard by the Supreme Court of Justice in the country.

First Quantum said last week the enactment of Law 406 marks the final step in revising the legal framework for the Cobre Panama mine.

President Laurentino Cortizo said on Sunday Panama would hold a referendum to decide whether to scrap a contract with First Quantum's local unit following days of protests by thousands of people opposed to the open pit copper mine project.

(Reporting by Arunima Kumar and Mrinalika Roy in Bengaluru; Editing by Shilpi Majumdar)