Peru's government has suspended civil liberties and called out the military in a highlands region after three people were killed and 23 injured in a clash between police and farmers over a Chinese-owned copper mining project.

The state of emergency imposed Tuesday is the second declared this year by Peru's government after fatalities in an anti-mining protest. It is to last 30 days.

Officials say violence broke out Monday when protesters encroached on the $7.4 billion Las Bambas project and police opened fire.

Health officials said most injuries were gunshot wounds suffered by protesters. Police Gen. Luis Pantoja told RPP radio that a police officer suffered a cracked skull.

The project is owned by a consortium led by China Minmetals Corp. It's Peru's largest and is to begin production in 2016.