President Ramzan Kadyrov of Chechnya has vowed to hunt down the killers of human rights activist Natalia Estemirova.
Ms Estemirova, a fierce critic of Mr Kadyrov, was abducted on Wednesday morning and shot.
According to the interior ministry, her body was later found in neighbouring Ingushetia with wounds to the head.
Ms Estemirova had been investigating human rights abuses in Chechnya for the Memorial group.
Her killing echoes the murder of a prominent journalist, Anna Politkovskaya, in 2006.
Colleagues of Ms Estemirova have blamed Mr Kadyrov's government for her death.
But he has vowed to bring her killers to justice, describing Ms Estemirova as a helpless woman.
