Human rights groups have called on the Central American government to investigate the deaths of dozens of peasants and campaigners in the Bajo Aguan area, in Honduras' northern Colon department.
"A long-simmering land conflict erupted in May 2011 when peasants occupied land being cultivated by large privately owned agricultural enterprises," says the pressure group Human Rights Watch in a report.
"Many victims were members of peasant associations who were allegedly gunned down by security guards working for the enterprises." ...
Antonio Trejo also spoke out against a government project to build privately run cities in Honduras, with their own police and tax system.
Just hours before being killed, Trejo had taken part in a televised debate in which he accused politicians of using such projects to raise campaign funds, says the AP news agency.
Honduras has the world's highest murder rate: 86 murders per 100,000 people.