Washington, July 16 (RIA Novosti) The White House has expressed sadness over the abduction and murder of Russian human rights activist Natalya Estemirova in the North Caucasus, and called on the Russian government to bring the killers to justice.

Estemirova, who had been investigating kidnappings and disappearances in Chechnya for the Memorial group, was kidnapped Wednesday morning in Grozny. Her body was found with bullet wounds later in the day in neighbouring Ingushetia. She was 50.

'We call upon the Russian government to bring to justice those responsible for this outrageous crime and demonstrate that lawlessness and impunity will not be tolerated,' White House National Security Council spokesman Mike Hammer told reporters.

Ian Kelly, a US State Department spokesman said in a statement: 'Estemirova was uncompromising in her willingness to reveal the truth regardless of where that might lead. She was devoted to shining a light on human rights abuses, particularly in Chechnya, and received a number of international awards for her brave work.'

Human Rights Watch has urged the Russian government to launch a full, transparent investigation into the murder.