The Sea Shepherd Conservation Society said that two of its volunteers were attacked by poachers on Playa Pacuare Thursday night.
A guard protecting the volunteers fired eight warning shots and then became a target of poachers who returned fire, the organization said.
A group of 11 volunteers were on the beach to protect nesting turtles and their eggs, the organization said.
Sea Shepherd said an estimated 10 poachers confronted the volunteers and attacked them with branches and machetes. The volunteers suffered minor injuries, the organization said.
A second guard was attacked by three poachers but managed to fend them off, said Sea Shepherd.
The organization said that the group was warned June 16 of a possible attack and reported these concerns to the Judicial Investigating Organization.