A 46-year-old farmer has been shot dead in Brazil's Para state in the Amazon, which has long been the scene of violent land disputes, a Catholic Church-linked observer body said Tuesday.

But Jose Batista — a lawyer for the Pastoral Land Commission, which monitors land disputes in the Amazon — said he could not say if the victim was directly involved in any conflict over land use and ownership.

"The police are investigating. We still don't have any information that would help confirm if this was due to a land dispute," said Batista.

The farmer was shot at point-blank range on Sunday when he was riding his motorcycle along a country path and stopped to open a gate, he said.

In May and June, six people were killed in Para and Rondonia, another Amazon state, including a couple of environmental activists who had denounced illegal logging in the area.

The Pastoral Land Commission has published a list of 125 activists and Amazon residents said to be on a death-threat list. The couple killed in May were on the list.

Although the government has taken urgent measures to protect the others, it has admitted that it does not have the means to guard all of them.

Friends and colleagues of the victims say powerful land barons have ordered the killings in retaliation for complaints by activists and poor residents about logging and ranching activities.

The commission estimates that 800 people have been killed in Para state over such disputes in the past four decades.

Last month, Amnesty International accused the Brazilian government of "failing in its duty to protect" the activists and locals, and "using the courts to harass them and criminalize dissent".