Hundreds of heavily-armed communist guerrillas have attacked three mining companies in the Philippines.

Philippine security officials are trying to verify reports that two or three civilian guards were killed in the raids on Monday.

The New People's Army guerrillas burned heavy equipment, disarmed guards and briefly held several people hostage.

One of the companies — the Taganito Mining Corporation — was forced to temporarily halt operations. The company is owned by Nickel Asia, which is partly owned by Japan's Sumitomo Corporation.

The Philippine government projects that mining investment will reach $18 billion by 2016, up from $3.8 billion over the past six years. The Philippines has vast untapped reserves of minerals, including gold, copper and nickel.

Maoists have been fighting to overthrow the government for more than 40 years. They continue their attacks, despite the resumption of peace talks earlier this year. An estimated 150,000 people have been killed in one of Asia's longest-running insurgencies.

The U.S. State Department lists the New People's Army as a terrorist group. It says the group routinely attacks businesses that refuse to pay extortion, or “revolutionary taxes.”