Interior Ministry officers stand guard at the site of a bomb explosion in Russia's southern city of Stavropol on Wednesday. ((Eduard Korniyenko/Reuters))

The death toll in a bombing in the southern Russia city of Stavropol has risen to seven, Russian officials say.

The bomb exploded Wednesday evening near a cultural centre, shortly before a Chechen dance company was set to perform there.

As many as 40 people were injured in the blast, the state-run news agency Ria-Novosti reported.

No group has claimed responsibility for the blast, which Russian officials have called a terrorist act.

Stavropol, which is on the northern edge of the Caucasus, has been largely free of the violence seen in Dagestan and Chechnya.

In March, two suicide bombers from Dagestan blew themselves up on the Moscow subway, killing 40 people and wounding 100.

Days later, a double suicide bombing in a small town in Dagestan killed 12 people, including the local police chief.

With files from The Associated Press