A regional investigator said the explosion outside the city's House of Culture and Sport, before a Chechen band concert, injured more than 42 people. The bomb was made of about a half-pound of TNT, the investigator said.
Officials said no one has claimed responsibility for the blast, Russian news agency RIA Novosti reported.
Officials said an 11 year-old girl was among the dead.
Stavropol Territory's health minister, Victor Mazharov, said at least 30 of the injured were hospitalized. Three were listed in critical condition.
Police found a bomb, a gun and ammunition during searches of the homes of two people suspected in the incident, RIA Novosti said. Authorities declared Friday as a day of mourning.