Three killed in Chechnya bomb attack
The attack, in a region where separatists have fought government forces for nearly a decade, took place as world leaders arrived in St Petersburg, at the other end of the country, for celebrations marking the 300th birthday of Russia's second city, hosted by President Vladimir Putin.
Security sources said the bus had dropped off about 20 workers after taking them to Khankala, the main Russian military base just outside the Chechen capital, Grozny.