Chile's Supreme Court Wednesday removed the last legal obstacle to building a giant $2.9 billion hydroelectric complex in the Patagonian wilderness, rejecting a bid by environmentalists to block it.

The highly controversial project, which environmentalists say will wreck a unique and pristine habitat in the southern tip of South America, sparked violent protests last year.

The high court "confirmed it was rejecting" an appeal by green campaigners to halt the $2.9 billion HidroAysen project of Spanish-Chilean consortium Endesa-Colburn, a court spokesman said.

The decision upheld an October 2011 finding by a lower court that gave the green light for the project to generate 2,750 megawatts of power from five dams in two river valleys in Patagonia.

The plans involve flooding 6,000 hectares (15,000 acres) of largely uninhabited land in a quest to generate more electric power for Chile's booming economy.

"The project is at a stage at which work is going on constantly," said HidroAysen attorney Mario Galindo. "There are studies, environmental impact studies... and it is all moving ahead normally."

But the project still needs approval from the government, after which construction would not begin until 2014, lasting about 10 years.

And environmentalists opposed to the plans said they would take their quest to derail the project to international bodies if needed.

Matias Asun of Greenpeace-Chile said "the project makes no sense environmentally. And it should not go ahead. So we will keep mobilizing alongside thousands of Chileans opposed" to it.

"Well, we are not happy with a negative ruling. But this is just a partial defeat," Patricio Rodrigo with No Dams in Patagonia told CNN Chile.

Attorney Marcelo Castillo said the ruling was already being reviewed with an eye toward seeking international court involvement in the case.