On Friday, December 27th, a car bomb exploded in the city of Pyatigorsk in the Stavropol Krai region, only about 170 miles from Sochi. A traffic police building was badly damaged and windows of buildings in the surrounding area were blown out. Three people were killed in the attack.

On Sunday, a suspected female suicide bomber killed at least 17 and injured about 50 people at a train station in Volgograd. Volgograd, formerly known as Stalingrad, is one of Russia’s largest cities. Volgograd lies about 400 miles away from the Olympic site at the resort city of Sochi.

Less than 24 hours after the train station bombing, a second suicide bomber destroyed a trolley bus in Volgograd, making it the city’s second attack in two days. The shrapnel bomb left mangled bodies in the street and 14 people dead.

Volgograd is a major transportation hub in the region, with bus routes and rail lines that go to the North Caucasus region where Sochi is located. The three attacks raise concerns about how Russia will handle security for the 2014 Winter Olympics.

Most likely, the culprits of the bombings were Chechens. Muslim Chechen separatists have been fighting for independence from Russia since the breakup of the Soviet Union in 1991. The First Chechen War lasted from 1994-1996 and the Second Chechen War from 1999-2009. Islamic insurgents have since been fighting an insurgency in the North Caucasus since 2009.

Chechen terrorists have been responsible for dozens of attacks in Russia, including the 2011 Domodedovo International Airport bombing and the 2004 Beslan School hostage crisis. Tamerlan and Dzhokhar Tsarnaev, the perpetrators of the 2013 Boston Marathon bombing, were also Chechens.

In July, Caucasus Emirate leader Doku Umarov called the Sochi Olympics “demonic dances on the bones of our ancestors.” The leader of the Islamist group also declared that insurgents would do “everything possible” to disrupt the Olympics.

In response to the terrorist attacks, Russian authorities have promised that every possible security measure has already been taken for the 2014 Winter Olympics, which are the most expensive Olympics on record. Russian Olympic Committee President Alexander Zhukov made a statement saying, “As for the Olympics, all necessary security measures have been taken. No additional security measures will be taken in Sochi … Everything necessary has been done.”

International Olympic Committee President Thomas Bach said, “I am certain that everything will be done to ensure the security of the athletes and all the participants of the Olympic Games.”