Ecuador has signed an agreement with a Chinese firm to begin exploiting a massive copper mine in the Amazon, prompting protests by environmental activists.

"We cannot be beggars sitting on a sack of gold," President Rafael Correa said at a signing ceremony Monday, adding that the deal would launch a "new era" of industrial mining in the small Andean country.

Police had earlier evicted a dozen female environmental activists who had occupied China's embassy to reject the pact with Chinese-financed mining firm EcuaCorriente (ECSA), saying it would damage the Amazon's fragile ecosystem.

The officers loaded the protesters onto a police bus surrounded by soldiers.

Yvonne Yanez, leader of the group Ecologist Action, said the activists entered the embassy without incident, and that the women had been waiting inside to deliver a letter to the ambassador, who never received them.

About 50 other activists were outside the diplomatic mission.

The mining "will affect for all time the territory of indigenous people and nature," the letter said.

"We reject the signing of the contract... without approval of an environmental impact study and without the knowledge of indigenous communities."

The agreement, which falls under a law passed three years ago, comes just before the main aboriginal group CONAIE planned to initiate a two-week march to Quito on Thursday to protest the mining and other Correa policies.

"We will not accept large-scale mining in our territory because it will destroy nature, pollute rivers and displace people in areas with significant agricultural potential, farming and tourism," CONAIE president Humberto Cholango told AFP.

ECSA plans to invest $1.4 billion during the first five years of the 25-year contract for the Mirador mine in the Condor range in southeastern Ecuador, in an area that the protesters say is one of the country's most biodiverse.

The mine has an estimated reserves of 2.1 million tons (4.7 billion pounds) of copper.

Ecuador stands to receive $4.5 billion over the term of the agreement, while the company, which will begin production in late 2014, will invest $100 million from royalties to help develop neighboring communities.

The state's share of mining income is 52 percent, higher than in countries like Chile (36 percent), Peru (32.9 percent) and Mexico (30 percent), but less than the 85 percent that applies to oil production.

"The state owns the resources and the company invests at a cost to get the resources. The highest percentage of profit will always go to the state," Vice Minister of Mines Federico Auquilla told El Comercio newspaper.

He said Ecuador has a dozen projects in advanced stages of exploration -- prior to signing an exploitation contract -- for copper, gold and silver.

But most of the projects are located in regions of the Amazon home to indigenous communities staunchly opposed to large-scale mining.