By VLADIMIR ISACHENKOVMOSCOW (AP) a¿¿ Two suicide bombings in as many days have raised concerns that separatist militants have begun a terrorist campaign in Russia that could stretch into the Winter Olympics in February. Russian authorities and the International Olympic Committee insisted the site of the games, protected by layers of security, is completely safe. The attacks in Volgograd, only 400 miles (650 kilometers) away from the Olympic host city of Sochi, reflected the Kremlin's inability to uproot Islamist insurgents in the Caucasus who have vowed to derail the games, President Vladimir Putin's pet project. No one has claimed responsibility for Sunday's blast at the Volgograd railway station or Monday's bus explosion there, but they came only months after Chechen rebel leader Doku Umarov threatened new attacks against civilian targets in Russia, including the Sochi Olympics. The two bombings killed 31 people and wounded 104, according to Russia's health ministry. As of late Monday, 58 victims were still hospitalized, many in grave condition. Suicide bombings have rocked Russia for years, but the insurgency seeking to create an Islamic state has been largely confined to the North Caucasus region in the past few years. The successive attacks in Volgograd signal that militants want to show their reach outside their native region. Matthew Clements, an analyst at Jane's, said Caucasus militants could be targeting major Russian transportation hubs like Volgograd to embarrass the Kremlin and discourage attendance at the Olympics, which begin Feb. 7. "The attack demonstrates the militants' capability to strike at soft targets such as transport infrastructure outside of their usual area of operations in the North Caucasus," he said in a note. "Although the very strict security measures which will be in place at the Sochi Games will make it difficult to undertake a successful attack against the main Olympic venues, public transport infrastructure in Sochi and the surrounding Krasnodar territory will face an elevated risk of attack."