Environmental activists say it is another attempt by the authorities to revive Rio Tinto's lithium exploitation plan in Serbia, despite previously stopping the project.

"Ecology is above all political directions and opinions, we need to raise awareness and protect it," protester Filip Filipovic, a 20-year-old student, told AFP.

The constitutional court, contacted by AFP, did not comment on whether the issue was on its agenda or not.

Meanwhile, Rio Tinto told AFP that they refrain from commenting on ongoing legal cases but confirmed they have used "available legal remedies in line with Serbian law".

"We have no knowledge nor are we informed about decisions of the constitutional court of Serbia regarding changes to the status of the 'Jadar' project", it said in a statement.

In January 2022, Belgrade revoked permits for the multibillion-dollar project that Rio Tinto, the world's second-largest metals and mining corporation, had hoped to develop in Serbia's western Jadar valley, known for some of Europe's largest lithium deposits

The then prime minister Ana Brnabic declared "all permits, resolutions and decisions related to Rio Tinto" project "invalid".

The decision followed massive demonstrations in Belgrade against the mine that activists label a permanent danger to the environment of the agricultural region.

Due to the government's decision Rio Tinto had to stop the exploitation of the land it owns in Serbia and addressed the court over the issue.

Opponents have also accused both President Aleksandar Vucic and Rio Tinto of not being transparent about the process.

Vucic, in an interview with the Financial Times in June, suggested that the lithium mine could start as soon as 2028, based on new assurances from Rio Tinto.

The statement stirred public concern and sparked a new wave of protests.

On Thursday, activists said they had demanded from the constitutional court for information regarding any initiative and its progress.

The court said it would reply within the "legal deadline" without elaborating.

According to Rio Tinto data, the mine in Jadar could produce 58,000 tonnes of lithium annually, sufficient for 1.1 million vehicles or 17 percent of Europe's EV production.

The mining giant recently published an environmental impact report aimed at assuaging concerns, saying the venture would rely on "safe, reliable, and proven technology".