Russia's North Caucasus region of Daghestan has declared May 5 a day of mourning after at least 14 people were killed in a double suicide bombing outside the republic's capital, Makhachkala.
Officials said the first blast occurred late on May 3 when an explosive device was detonated inside a car that had stopped at a police checkpoint outside Makhachkala.
A second bomb was detonated inside a minivan at the same site some 25 minutes later, hitting troops and investigators who responded to the initial blast.
More than 100 people were injured.
Daghestan's Interior Minister Abdurashid Magomedov has blamed Islamic militants for the attack.
Health officials say two suspected suicide bombers, one male and one female, are among the dead.
Shoot-outs and bombings between suspected Islamic militants and security forces in the North Caucasus cause scores of casualties each year.
Outgoing Russian President Dmitry Medvedev has called the North Caucasus the key security challenge for the country.
Based on reporting by Reuters, ITAR-TASS, and Interfax