More than 15,000 Romanians took to the streets for the eighth straight day Sunday to protest a Canadian company's plans to open Europe's largest gold mine in a picturesque Transylvanian village.

Canadian firm Gabriel Resources hopes to extract 300 tonnes of gold in Rosia Montana in the Carpathian mountains with mining techniques requiring the use of thousands of tonnes of cyanide.

In Bucharest, around 8,000 people marched or rode their bikes to the government headquarters chanting "United we can save Rosia Montana".

Many students as well as young couples with babies were among the protesters.

Carrying banners reading "I love nature, not cyanide" and "Corruption equals cyanide", they called for the resignation of Prime Minister Victor Ponta, whose government last month adopted a bill clearing the way for the open-cast mine.

The draft law still has to be approved by parliament.

Around 6,000 protesters also rallied in Cluj, the major Transylvanian city, and around 900 in Brasov, police said.

Protests were also staged in several other towns.

"We are calling on the government to withdraw this draft law without delay," said Tudor Trif, a 29-year-old engineer marching alongside his wife and son.

"We cannot bequeath to our children a lake full of cyanide and a polluted region," he told AFP, referring to the huge tailings lake where used water from the gold mine will be stored.

"It's the first time that young Romanians rally against a project threatening the environment, I find it quite encouraging," singer Mihaela Mihai, 66, told AFP.

Gabriel Resources, which owns 80 percent of the Rosia Montana Gold Corporation, acquired a mining licence in 1999 but has been waiting ever since for a crucial permit from the environment ministry.

The company promises 900 jobs during the 16-year extraction period and economic benefits.

Opponents say the mine will be an ecological time-bomb and threaten the area's Roman mining galleries.

The project will also lead to the destruction of four mountains and require hundreds of families to be relocated.