UNESCO added the ancient Roman gold mining area of Rosia Montana in western Romania to its list of world heritage sites on Tuesday, throwing the town a lifeline and further complicating a long-stalled mine project.

Canada's Gabriel Resources, which had planned to build Europe's largest open cast gold mine in Rosia Montana, is currently seeking $4.4 billion in damages from Romania for losses related to its stalled project at the World Bank's International Center for Settlement of Investment Disputes.

The government, which has a 20% stake in the project, officially withdrew its support for the mine in 2014 after months of country-wide street protests against it. The company gained concession rights to the area in 1999.

"With joint efforts from officials and specialists Rosia Montana must become a role model of showcasing the patrimony through sustainable development," Romanian President Klaus Iohannis said on Tuesday, saluting UNESCO's decision.

The town, which has few employment options and poor infrastructure, could see an inflow of funds after UNESCO's decision, officials said.

Not everyone was pleased. Rosia Montana's mayor Eugen Furdui, a long-time supporter of the mining project, said the decision only brought additional conservation costs.

The European Union state first put the ancient Roman mine tunnels and vestiges up for inclusion on the world heritage list in 2016.

(With input from agencies)