RIO DE JANEIRO (Thomson Reuters Foundation) - The escalation of violence against land rights activists in Brazil is of “deep concern”, the United Nations’ environment chief said on Wednesday, calling for a full and impartial investigation into the recent killings of three of them.

Erik Solheim, executive director of UN Environment, said land rights that are guaranteed under the Brazilian constitution must be implemented by government and respected by businesses.

“UN Environment notes with deep concern the escalation of violence against land rights activists in Brazil,” Solheim said in a statement.

“The recent murder of Nazildo dos Santos and two other environmental activists in the state of Para is indicative of a worrying pattern of retaliation against those protecting their environmental and human rights,” Solheim said.

The government was not immediately available for comment.

Brazil is rich in land ripe for development and low on deeds and property records, leading to widespread tension and conflict.

Nazildo Dos Santos Brito, 33, the head of a community association of farmers and quilombolas, as slave descendants are known, was killed earlier this month in northern Para, police said.

He was the subject of lawsuits filed by palm oil company Biopalma da Amazonia SA, a subsidiary of giant mining company Vale, which accused him of disturbance, invasion, threats and other crimes, according to local media.

Solheim called for a “full, transparent and independent investigation” into the murders of dos Santos and two other land activists in Para state since December.

“The murder of indigenous people living on the front lines of environmental protection is unacceptable,” said Solheim.

Brazil was the world’s most dangerous nation for land rights activists in 2016, with about 50 people killed, according to London-based advocacy group Global Witness.

The Pastoral Land Commission, an organization associated with the Catholic Church in Brazil, said 70 people were killed over land and environmental disputes in 2017, the most since 2003. Para state led with 21 of the murders.