VOLGOGRAD, RUSSIA

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 34 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 said more than 5,200 security forces are deployed in the city of 1 million.

The Health Ministry said three more victims died today, raising the toll to 34 — 18 from the station bombing and 16 from the bus. Officials said 65 other people were hospitalized with injuries.

Volgograd authorities have canceled mass events for New Year’s Eve, one of Russia’s most popular holidays, and asked residents not to set off fireworks. In Moscow, festivities were to go ahead but authorities said security would be increased.

There has been no claim of responsibility for either bombing, but they came only months after the leader of an Islamic insurgency in southern Russia threatened new attacks on civilian targets in the country, including on the Winter Games that are to begin Feb. 7 in Sochi.

Games organizers have introduced some of the most extensive identity checks and security measures ever seen at an international sporting event. But even if security at the Games themselves is tight, many analysts suggest that public transit in Sochi and sites away from the sports venues are vulnerable.

Suicide bombings have rocked Russia for years, but the insurgents seeking to create an Islamic state have largely confined their attacks to the North Caucasus region in recent years. The blasts in Volgograd signaled that militants want to show their reach outside their native region. Volgograd is about 300 kilometers (200 miles) north of the Caucasus and about 690 kilometers (430 miles) northeast of Sochi.

China, host of the 2008 Summer Olympics, today expressed confidence in the security of the Sochi Games.

“The competent authorities on our side have maintained close communication and cooperation with Russia in terms of the security work for the Winter Olympics. We believe that Russia is capable of ensuring security and hosting a successful Winter Olympics,” Foreign Ministry spokeswoman Hua Chunying told reporters today.

The United States would welcome “closer cooperation” with Russia on security preparations for the Winter Olympics, White House spokeswoman Caitlin Hayden said Monday.

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