Thousands of police officers and paramilitary forces are on duty in the Russian city of Volgograd, which is reeling from two suicide bombings in two days that killed 33 people and raised fears that a terrorist campaign may have begun that could stretch into the Winter Olympics.

In the wake of Sunday's bombing at the city's main railway station and Monday's blast on a trolleybus, police reinforcements and Interior Ministry troops have been sent into the city, regional police official Andrei Pilipchuk was quoted as telling the Interfax news agency. He says more than 5,200 security forces are deployed.

The Emergencies Ministry said two more victims died on Tuesday, raising the toll to 33 — 18 from the station bombing and 15 from the bus.