The UN, EU and other international organisations have condemned the murder on Wednesday of a prominent environmental activist in Honduras.
Lesbia Yaneth Urquia was killed four months after the shooting of award-winning environmentalist Berta Caceres.
Both women had spent years campaigning against a giant dam.
More than 100 people have died in Honduras in five years for opposing dams, mining, logging and agriculture projects, human rights groups say.
In a statement, the EU said urgent steps needed to be taken to fight impunity and protect human rights activists.
"This killing as well as the climate of violence that continues to prevail over human rights activists in the country is an extremely worrying development," it said.
The body of Ms Urquia, 49, was found abandoned on a rubbish dump in the municipality of Marcala about 160km (100 miles) west of the capital, Tegucigalpa.
A mother of three children, she was a member of the Council of Indigenous People of Honduras (Copinh) - the organisation founded by Caceres - and had been working to stop a hydroelectric project in Honduras's western La Paz department.
Copinh said in a statement on its website: "The death of Lesbia Yaneth is a political femicide that tries to silence the voices of women with the courage and bravery to defend their rights."
"We hold the Honduras government directly responsible for this murder."
Judicial officials said on Thursday they had opened an investigation into the killing.
Violence in Honduras has increased since July 2009 when President Manuel Zelaya was forced from power.
A new right-wing government licensed hundreds of infrastructure projects including mines and hydroelectric dams in environmentally sensitive areas.
In the US, politicians have been expressing concern about the violence.
Last week, Congressman Hank Johnson put before the House of Representatives the Berta Caceres Human Rights Act, which would suspend US security assistance until human rights violations by security forces ended.