The second suicide bomb attack in two days hit the southern Russian city of Volgagrad, killing 14 and wounding dozens more. The target was a trolleybus. Yesterday's attack was at the rail station.

The attacks call into question Russian security efforts in advance of the Sochi Olympics scheduled to being in early February.

CNN:

Another deadly blast has struck the southern Russian city of Volgograd, killing at least 14 people and further highlighting Russia's security challenges as it readies to host the Winter Olympics in less than six weeks.

An explosion hit a trolleybus near a busy market during the morning rush hour Monday, a day after a blast at Volgograd's main train station killed 17 people and wounded at least 35 others.

Like Sunday's attack, the blast Monday was a terrorist act, Vladmir Markin, a spokesman for the country's federal investigation agency, told the state-run news agency RIA Novosti.

No one claimed responsibility for the explosions. But they come several months after the leader of a Chechen separatist group pledged violence to disrupt the 2014 Sochi Winter Olympics.

Video footage from the scene Monday showed the twisted shell of the blue trolleybus, with debris spread around it. The impact of the blast blew out the roof of the bus, as well as windows of several nearby houses. At least 28 people were reported to be wounded. Several are in serious condition, including a 6-month-old baby, RIA Novosti reported.

Based on the footage, the blast appeared to have occurred in the back half of the bus. The federal investigation agency said it believes the explosion was set off by a male suicide bomber.

And there are strong indications the two attacks are linked, the agency said.

Investigators said the train station blast Sunday appeared to have been caused by a suicide bomber, who may have been female.

Markin told RIA Novosti that DNA testing will be carried out on the remains of the station bomber, who used the equivalent of 10 kilograms (22 pounds) of TNT in a device containing shrapnel. Investigators say they also found an unexploded grenade at the scene.

Video taken from an outside security camera shows a huge fireball inside what appears to be the main entrance of the three-story stone building, followed by a steady trail of smoke coming out of shattered windows.

Sochi is 640 miles from Volgagrad, but it's possible that the terrorists are testing methods and modes of attack, priming themselves for something really big when the games get underway.

Some security experts think the Russians aren't up to it. You would think in an authoritarian country like Russia, security would be a strong point. But in this case, there are so many soldiers, secret police, police, and other security personnel that there may be problems in coordinating such a massive force.

A few more bombs like these two and there are likely to be a trickle of cancellations to the Olympics.