Death tally could still go up, depending on injuries.
At least two "devices" detonated, at least one reported as having "shrapnel" (in the sense of intentional shrap, not accidental), another one or two devises defused. Putin was reportedly in the city (though not threatened).
I can't find a good article link yet, just early development pages.
(I realize that's the British branch of the Russian RT. It's provided for context of how checking their government spin.)
Such a terrible thing. My prayers go out to the victims and families.