Three more people have been killed at the Grasberg mine -- one of the world's largest -- in Papua, taking the death toll during a strike to seven.

Unidentified gunmen killed three people near the mine in Indonesia's restive Papua province, a report by the state news agency Antara said. One of the dead was a contract worker who had worked at the mine for 20 years.

Operations have been severely cut back since Sept. 15 when workers began a strike at the copper and gold mine, run by PT Freeport Indonesia, a division of Freeport-McMoRan, which has headquarters in Arizona.

The open pit mine forms a 1-mile-wide crater and is the world's third largest producer of copper. The low-cost labor setup has around 20,000 employees.

But Papua province is in one of Indonesia's most politically sensitive and remotest areas. The province is about the size of Spain and occupies the western half of the island of Papua. Papua New Guinea occupies the eastern half.

Papua has been a part of the Indonesian archipelago federation since the Dutch gave up their colonial rule and a slim majority in a controversial referendum in 1969 voted in favor of joining.

Papuans are ethnically Melanesian and closer to Australia's aborigines than the Asians who make up most of Indonesia's population. Papuans say their culture and identity is being eroded by an influx of Asian Indonesians.

As with many of Indonesia's governments, that of President Susilo Bambang Yudhoyono has been faced with a Papuan independence movement. The struggle periodically erupts into deadly attacks on security forces and employees at the mine, as well as brutal attacks by police on demonstrators.

A shootout at the mine by suspected members of the Free Papua Movement in July 2009 left three people dead, including Australian technician Drew Grant, 29, a project manager at the mine. He was killed when the vehicle he was driving was ambushed.

FPM denied it was involved.

The next day an Indonesian security guard was killed in another attack and a police Mobile Brigade officer who went missing during a third attack was found dead in a ravine near the ambush site.

There are persistent allegations that members of the military and police are fighting over multimillion-dollar protection contracts for mine employees.

In the current strike at the Grasberg mine, workers are blocking main roads from Porsite Harbor to Timika, Kuala Kencana and Tembagapura. This has cut off food, production equipment, medicine and other supplies needed for mine operations.

There have been reports of striking workers intimidating other workers on their way to the mine and outside working hours at public places, including the bus terminal, Antara said.

Last week a spokesman for mine made a plea for the workers to end the strike, saying there is the danger of closure of the project.

But the owners also back the police as they try to improve the security situation, said PT Freeport Indonesia spokesman Ramdani Sirait.

"PTFI fully supports and cooperates with the security personnel to investigate the incidents. Such actions must be stopped and civil order must be restored," Sirait said.

"And most importantly, they must be responsible for the illegal acts and face the consequences. Striking workers who are involved in those actions have violated basic human rights and criminal laws."

Talks continue between the company and the mine workers' union, the BBC said.

The union wants a five-fold pay increase on their wages of $3.50 per hour. They say the increase would put the Papuan workers' pay in line with that of other PTFI mine-workers around the world.