The first signs of domestic discontent are surfacing for Prime Minister Alexis Tsipras as his anti- austerity government braces for the first protest rally in Greece since he came to office three months ago.

About 4,000 miners and their families descended on Athens' main central square on Thursday over a plan to possibly revoke the license of a gold mine in the north of the country, which would halt investment in the project.

"The government needs to decide and give a clear answer" on the future of the mines, Giorgos Hatzis, a spokesman for workers, said on Skai TV. "We will only back down when the prime minister himself comes out and says that this investment is legal and can continue."

It's the first mass street protest against the government since the Jan. 25 ballot that catapulted Tsipras to power. While opinion polls still show Syriza enjoys a solid lead over opposition parties, and the majority of Greeks support its refusal to implement austerity measures attached to the country's bailout, the gathering suggests blanket public support for Tsipras's policies may be waning.

"The honeymoon is over" said Nikos Marantzidis, a pollster and political science professor at the University of Macedonia. "This doesn't mean that Syriza's hegemony is under dispute but we're done with the period when Greek public opinion would agree with everything that the government does."

Anti-Government Slogans

Miners are holding the rally after the government decided to rescind environmental permits for a processing plant at a Eldorado Gold Corp.-operated mine in Skouries. The decision threatens to stall a $1 billion investment project that could create 5,000 jobs, according to the company's website.

As miners shouted anti-government slogans outside the parliament, victims of terrorist attacks protested inside the building against a bill submitted by the justice ministry that would pave the way for the release of a convicted assassin from prison.

Savvas Xiros, who has been sentenced to life imprisonment for killing five people as a member of the guerrilla group November 17, may spend the rest of his sentence detained at home if the bill allowing prisoners with severe disabilities to exit jail under certain restrictions passes. Xiros was maimed after a bomb he was about to plant in 2002 exploded in his arms.

"The case of Xiros would be irrelevant in itself," Marantzidis said. "But in conjunction with other moves, it reinforces the perception that the government is soft on crime."

A majority of Greeks opposed a decision to allow undocumented migrants to leave a detention center on the outskirts of Athens, Marantzidis said. The government has also said it will revoke legislation establishing high security prisons, as protesters opposing these facilities have been occupying the central building of the University of Athens for over two weeks.