An indefinite strike at Peru's largest port, Callao, has caused the country economic losses of more than US$100 million, the main exporters association said Tuesday.

The 23-day strike began after operators of APM Terminals introduced a new electronic system for selecting shifts that aims to help police investigate drug smuggling.

The union previously picked shifts. APM Terminals, the operator of the port's North Pier since April 2011, operates the northern terminal, which handles 75 percent of Callao's capacity.

In response to workers demands, APM Terminals fired 130 striking workers, which the company claims was legal under Peruvian labor laws.

The latest industrial action, which involved over 700 workers, marks the sixth strike at the port over the last nine months.

Telesur