Honduras and Guatemala are the most dangerous countries in the world for environmentalists due to the persecution and even murder of activists, Amnesty International said in a report Thursday.

The London-based global rights group pointed to "an insidious wave of threats, bogus charges, smear campaigns, attacks and killings of environmental and land activists in recent months" in the Central American countries.

Amnesty's report looks at the plight of "individuals and communities fighting to protect the environment from large-scale mining, logging and hydroelectrical projects" in the region.

For AI Americas Director Erika Guevara-Rosas, the murder in March of Honduran environmentalist Berta Caceres "seems to have marked a deadly turning point for human rights defenders in the region.

"The lack of a transparent and effective investigation into her killing has sent the abhorrent message that shooting someone, point blank, for standing up to powerful economic interests is actually allowed," she said.

In Guatemala, the report said activists "have been constantly subjected to smear campaigns aimed at stigmatizing and discrediting them in order to force them to stop their legitimate work."

The smears include "being falsely accused and prosecuted as a way of keeping them silent," AI said.