Geneva  - The top United Nations official on human rights said Thursday that the investigation into the killing of Natalya Estemirova must be "thorough, transparent and independent."

Estemirova, a prominent human rights activist working on issues relating to Chechnya - where she lived - was kidnapped and shot to death on Wednesday, her body turning up in neighboring Ingushetia.

The UN High Commissioner for human rights, Navi Pillay, noted that Moscow ordered an investigation, and said the authorities must "do all they can to ensure that the perpetrators are prosecuted and brought to justice."

The work of human rights activists in Russia "is precarious," Pillay said.

"Estemirova's death is the latest in a series of killings or attacks against human rights defenders, journalists and lawyers in the country," the high commissioner's office commented in a statement.

The latest death followed the slayings of two of Estemirova's colleagues, the journalist Anna Politkovskaya, who was shot dead in 2006, and the activist Stanislav Markelov, killed earlier this year.(dpa)