Romania's government faced mounting opposition Friday from rights groups and artists over a draft law clearing the way for a Canadian gold mine project slammed as environmentally harmful.

Canadian company Gabriel Resources, through its 80-percent owned subsidiary Rosia Montana Gold Corporation, plans to open Europe's largest open-cast gold mine in the Transylvania region, mining gold and silver using thousands of tonnes of cyanide.

The project will destroy four mountains tops around the picturesque village of Rosia Montana, and archaeologists warn it will also destroy unique Roman mining galleries.

Last week, Romania's centre-left government approved a bill making it easier for the company to expropriate people's property and granting "exceptional national interest status" to the mine, which aims to extract 300 tonnes of gold and 1,600 tonnes of silver.

The legislation, which still needs parliament's approval, contains a rise in royalties for the Romanian state and stricter environmental protection guarantees, the government stressed.

"We call on the government to withdraw this draft law... which violates property rights as well the right to live in a clean environment," Alexandru Riza, campaign coordinator for Greenpeace, told AFP.

More than 6,500 people have signed the group's call.

The Alliance for a Clean Romania, a major rights group, also asked the government to withdraw the bill.

Hundreds of Romanians have signed their online petition, including director Corneliu Porumboiu, winner of two prizes at the Cannes film festival, contemporary artist Dan Perjovschi and Cristina Flutur, who won the Cannes best actress prize in 2012 for her performance in "Beyond the Hills".

"I love nature, I love Romania and I think we can make a change. We cannot tolerate such abuses anymore," Flutur told AFP while taking part in the daily street protests organised in the centre of Bucharest against the mine.

Thousands have taken to the streets of Romania's main cities since Sunday to defend the village of Rosia Montana.

"The site boasts invaluable archaeological remains dating from the Roman era," Stefan Balici, vice-president of the Architecture, Restoration, Archaeology Association, told AFP.

"If the project goes ahead it would be a cultural crime, an invaluable loss," he added.

Balici said that his association, which works together with the Alburnus Maior group representing villagers opposed to the project, will do its best to block it.

But Gabriel Resources said the project would "clean up centuries of historic pollution and meet or exceed the latest European Union and Romanian laws on environmental protection... and restore and protect the heritage of the historic town of Rosia Montana, which currently lies in a state of continuing decay."

The company promises 900 jobs in the 16-year extraction phase and say the mine would "provide substantial economic, environmental, cultural and social benefits to the region and ...the local community."

However, the government's bill was criticised by the Ministry of Justice which drew up an 18-page document summarising its comments.

The ministry said that several articles describing the way expropriations are to be conducted were "unconstitutional" and slammed the numerous exceptions to legislation currently in force that the company will benefit from.

It also stressed that laws are texts of "general applicability" and should not simply approve a contract between two parties, as the government's bill does.

Prime Minister Victor Ponta said his government had taken into account all these comments when it drew up a new version of the bill, but analysts noted that several of the contested stipulations had not been amended.

"The draft law was submitted to parliament although the justice ministry warned that it could be declared non constitutional," Gandul daily wrote Friday.