Anglo said it was not certain who the protesters were. The latest seizure immediately followed what Anglo called an agreement between companies it uses to provide services at the mine and the Federation of Contract Workers union.

But the union indicated that it was not satisfied, and would continue to demand better contracts for workers, blaming Anglo American for an "insufficient" offer given the rise in the company's shares, which spiked with the price of copper after Donald Trump's surprise victory in the U.S. presidential election earlier this month.

"Anglo American presented a proposal that was far from the interests of workers," the union said in a statement Saturday.

Anglo American said it requested help from authorities and was preparing legal action to ensure the protection of its workers and property.

The company "makes a new call to suspend this illegal seizure and hold dialogue through established channels," Anglo American said.

Hooded protesters also took control of Los Bronces on Nov 16, prompting the company to suspend operations and evacuate 1,500 workers. Operations restarted the following day.

Anglo American's Sur unit, comprising Los Bronces and the El Soldado mines, produced about 30,000 tonnes of copper per month in the first three quarters of 2016.

(Reporting By Fabian Cambero; Writing By Mitra Taj; Editing by Jonathan Oatis and Bill Rigby)

By Fabian Cambero