A powerful bomb destroyed a bus in the Caucasus Mountains city of Nalchik on Friday, killing five people and wounding 18.
The bus had just arrived from the town of Mineralnye Vody, which has been the site of previous attacks in the restive Caucasus region.
A spokesman for the Federal Security Service, Alexander Zdanovich, blamed the explosion on a bomb that ignited a fire, the Interfax news agency said.
Authorities said there was no immediate claim of responsibility and the motive was not known.
Nalchik, capital of southern Russia’s Kabardino-Balkaria region, is about 700 miles south of Moscow.