At least one person has been killed after a bomb was detonated at a police checkpoint in the southern Russian region of Ingushetia.
Five other people were wounded in the blast in Nazran, the area's main city, Russian news agencies reported.
Police suspected Friday's attack had been carried out by a suicide bomber.
The state-controlled RIA news agency, quoting the Ingush interior ministry, said the dead person was a civilian.
Yunus-Bek Yevkurov, the leader of Ingushetia, told the Interfax news agency that he had instructed authorities in the region to step up their readiness following the attack.
"The atmosphere is very uneasy... It will be controlled by law enforcement agencies," he said.
Southern Russia's Caucasus region has experienced a rise in the number of bombings and armed attacks recently after several years of calm that followed two separatist wars in Chechnya, Ingushetia's neighbouring region.
Yevkurov and Ramzan Kadyrov, the Kremlin-backed leader of Chechnya, have warned Dmitry Medvedev, the president, that the separatist violence is widespread and they are struggling to contain it.
Last month, at least 21 people died in an attack on a police station in Ingushetia, and in June a suicide bomber almost killed the region's president.
Regional leaders have claimed that the attacks are the work of Islamist separatist fighters.