Many targeted had been carrying out work related to the human rights situation in the North Caucasus republic of Chechnya, such as Estemirova, the seven experts said in a statement.
Urgent action was needed to break a "cycle of impunity" which has meant the perpetrators of previous crimes have not been brought to justice, they added.
The experts said Russian assurances on catching Estemirova's killers meant little unless authorities investigated her murder more seriously than previous crimes.
They also pointed out Russia had a "prime responsibility" to protect human rights activists.
Estemirova, 50, was found dead last Wednesday with gunshot wounds to the head and chest hours after she was seen being bundled into a car outside her home in the Chechen capital Grozny.
She was one of Russian rights group Memorial's main employees in Chechnya and had won worldwide acclaim for uncovering rights abuses.
Her death prompted tributes from around the globe and calls on Russia to find the killers.
Estemirova was a close associate of Russian journalist Anna Politkovskaya, who was assassinated in 2006 in Moscow and was also well-known for her human rights work in Chechnya.
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Urgent action was needed to break a "cycle of impunity" which has meant the perpetrators of previous crimes have not been brought to justice, they added.
The experts said Russian assurances on catching Estemirova's killers meant little unless authorities investigated her murder more seriously than previous crimes.
They also pointed out Russia had a "prime responsibility" to protect human rights activists.
Estemirova, 50, was found dead last Wednesday with gunshot wounds to the head and chest hours after she was seen being bundled into a car outside her home in the Chechen capital Grozny.
She was one of Russian rights group Memorial's main employees in Chechnya and had won worldwide acclaim for uncovering rights abuses.
Her death prompted tributes from around the globe and calls on Russia to find the killers.
Estemirova was a close associate of Russian journalist Anna Politkovskaya, who was assassinated in 2006 in Moscow and was also well-known for her human rights work in Chechnya.
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