Thousands of people marched Sunday against a Canadian company's plans to open Europe's largest gold mine at Rosia Montana, in what has become one of the longest-running protests in post-communist Romania.

The movement started a month ago after the Romanian government adopted a draft law clearing the way for a controversial open-cast gold mine planned by Canada's Gabriel Resources in the heart of Transylvania.

The company, 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.

In Bucharest, around 4.000 people marched despite the rain chanting "United we can save Rosia Montana" and carrying Romanian flags.

"I am here in defence of the environment and the cultural heritage of Rosia Montana but also because I am sick and tired of the way politicians treat us," said one of the protesters, Otilia Dumitrescu, a 62-year-old retired architect.

Gabriel Resources hopes to extract 300 tonnes of gold with mining techniques requiring the use of thousands of tonnes of cyanide.

It promises 900 jobs during the 16-year extraction period, as well as economic benefits.

But academics and environmentalists say the mine is an ecological time bomb and threatens the area's Roman mining galleries.

The protesters also chanted slogans against plans by US energy giant Chevron to dig for shale gas in eastern Romania using the controversial "fracking" technique that threatens to contaminate ground water.

"We will continue to stage protests because we want to save Romania," said an Orthodox priest, Iulian Ghimus, 53.

Some 2,000 protesters also rallied in Cluj, chanting "Rosia Montana is the heart of Romania".

"Even if turnout is lower because of fatigue and bad weather, the people's message is clear: they will keep on protesting until the Rosia Montana project is withdrawn and a law banning environmentally harmful mining projects is adopted," sociologist Mircea Kivu told AFP.

Kivu added that protesters have also signalled that "they want a change in the way Romanian politics is conducted" after more than 20 years of corruption and scandals related to cronyism.