At least two people were shot and killed and 18 wounded in a clash between police and local farmers protesting a $7.4 billion Chinese-owned copper mining project, health officials said Monday.

"The two men died of bullet wounds. One was age 30, the other age 24," said Percy Jeronimo, the oral surgeon running the emergency room in the local health clinic. He said four of the wounded were in critical condition.

Police apparently opened fire on the protesters when they entered part of the Las Bambas mine where the plant that separates copper ore from rock is under construction.

The local health director, Jose Soplopuco, told The Associated Press that ambulances can't reach Challhuahuacho, the town of about 20,000 residents where the clinic is located, because police had shot at a vehicle carrying doctors.

The Las Bambas project is owned by a consortium led by Chinese state giant China Minmetals Corp. It is scheduled to begin production in 2016 and produce 400,000 metric tons of copper the following year.

President Ollanta Humala appealed to protest leaders for calm. He called Las Bambas Peru's biggest mining project on Monday.

The Associated Press called the project's office in Lima but no one answered.

Peru is the world's No. 3 copper producer and mining accounts for about 60 percent of its export earnings.

But resistance by local farmers has frustrated and delayed major projects across the rugged Andean nation. Six people have been killed so far this year in anti-mining protests, including a police officer whose skull was fractured during May resistance to a Mexican-owned copper mining project.