Russian President Vladimir Putin has made a visit to the city reeling from two suicide bombings this week, saying such attacks are indefensible.

The bombings at the main railway station of Volgograd and on a city trolleybus killed 34 people and wounded scores, 65 of whom are hospitalized.

No claim of responsibility has been made for either attack, but they come a few months after the leader of an Islamic insurgency in Russia's south called for attacks in the run-up to February's Winter Olympics in the resort city of Sochi.

Putin, opening a meeting before dawn Wednesday in Volgograd with the heads of the Federal Security Service and the Interior Ministry, said: "Whatever motivated the criminals' actions, there's no justification for committing crimes against civilians, especially against women and children."