Greenpeace activists stormed Romania's Environment Ministry on Tuesday, chaining themselves to radiators in the minister's office in an attempt to stop approval for Europe's biggest open-cast gold mine in a small Carpathian town.

A decision is due soon on whether to award an environmental permit to the project, which aims to use cyanide to extract 314 tonnes of gold and 1,500 tonnes of silver in the western Romanian town of Rosia Montana.

About 20 Greenpeace activists from Romania, Hungary, Germany, Austria, Italy and Slovenia descended on the ministry in central Bucharest. Wearing bright yellow jackets, they knelt silently or sat on the dark red carpet of Environment Minister Laszlo Borbely's office, holding banners saying Save Rosia Montana and No cyanide at Rosia Montana.

The project, which has been on the drawing board for 14 years, is led by Rosia Montana Gold Corporation, majority-owned by Canada's Gabriel Resources Ltd with the Romanian government holding 19 percent. The company has valued the project at $7.5 billion.

Over the years, it has drawn fierce opposition from civic rights groups, environmentalists and neighbouring Hungary, who say it would destroy ancient Roman gold mines and villages, and could lead to an ecological disaster.

There is no environmentally feasible way to use cyanide technology. We don't want a catastrophe in Rosia Montana, Gergely Simon, a Budapest-based toxic expert for Greenpeace, said outside the ministry.

Small protests were also planned at Romanian embassies in Sofia, Vienna, Budapest and Warsaw with activists handing out barrels of dead fish and petitions to ban cyanide mining in Romania.

Gold Corporation proposes four gold quarries which would destroy four mountaintops and wipe out three villages of Rosia Montana's 16 while preserving the historical centre.

President Traian Basescu, who has been rocked by anti-government protests this month, backs the project and says it will bring much-needed foreign investment.

At the weekend, hundreds of people protested in Bucharest against the plan while in Rosia Montana, most of whose 2,800 residents hope it will bring jobs and money to their impoverished town, a similar number rallied in support.

They didn't scare me, Environment Minister Borbely told reporters. I told them I will not propose this project to the government for approval unless I am 100 percent convinced it will not harm the environment.

The project is not in its final stages, it is under analysis with a technical committee ... but I cannot say at this moment it will reach a conclusion in February.