LIMA: A weekend attack on a copper project in northern Peru that left three dead may have been the work of drug traffickers who want to keep the area undeveloped in order to protect their trade, the head of a business leaders group said on Tuesday.

The Rio Blanco copper project, owned by China's Zijin Mining Group, on Sunday was invaded by 15 to 20 gunmen who fired at employees - killing three - and then set the complex ablaze, the company said.

Opium poppies cultivated for the heroin trade are grown in the mountainous area.