Washington, Aug 12 (DPA) The US called on Russia Tuesday to rigorously investigate the murders of a human rights activist and her husband in Chechnya.

'It's important that the Russian government vigorously and immediately investigate these appalling crimes and bring those who are responsible to justice,' US State Department spokesman P.J. Crowley said.

The bodies of prominent activist Zarema Sadulayeva and her husband, Alik Djibralov, were found shot to death in the trunk of a car Tuesday, one day after they vanished.

They are the latest of a string of attacks against human rights proponents. The US in the past has criticised Moscow for being too slow to thoroughly investigate murders of journalists or activists at odds with the Kremlin.

'We do have deepening concern about the violence of those who are advocating human rights, the rule of law, and independent media and humanitarian assistance in the North Caucasus,' Crowley said.