Around 500 indigenous Lenca people held a protest in Honduras' capital on Wednesday demanding an international probe into the March murder of a widely respected activist from their community, Berta Caceres.

Organizers said they had no confidence in Honduran authorities handling the task because they had tried to make social movements like the one Caceres led illegal.

Two masked gunmen fatally shot Caceres, a 45-year-old activist for indigenous, environmental and social issues, at her home in La Esperanza, northwest of the capital Tegucigalpa on March 3.

Five people were arrested last month in connection with the murder.

One of the detained suspects is a high-ranking employee of Desarrollos Energeticos (DESA) -- an electricity company involved in the construction of a hydro-electric dam against which Caceres had campaigned.

Before her death, Caceres said she had been threatened by DESA for organizing local resistance to the Agua Zarca dam.

Her family has expressed concerns that the suspects arrested might never face justice. It has called for the Inter-American Commission on Human Rights, an autonomous body in the Organization of American States (OAS), to have access to Honduras' investigation.

Wednesday's protest, which converged on the public ministry in charge of prosecutions, sought the establishment of an independent commission made up "an international and impartial group of experts," according to a statement by organizers.