At least 18 people were killed Sunday morning in a bombing at a train station in Volgograd, in southern Russia, according to officials. Dozens more were wounded. A video shows the moment of the blast.

Reports cited Russian security personnel as saying the blast was a suicide bombing. The bomber was apparently female.

Seven people died in a similar suicide bombing in the same city in October. In that attack, a female bomber blew up a passenger bus, killing six people and wounding 33 more.

Late last week three people were killed in a bombing in the city of Pyatigorsk, also in southern Russia.

The attacks come as Russia is preparing to host the 2014 Winter Olympics in Sochi. The Olympic games are scheduled to begin in just over five weeks.

Chechen terrorists are apparently behind the latest attacks. Chechen leader Doku Umarov recently urged terrorist groups to use “maximum force” to prevent the Olympic Games. Islamist leaders in Syria have similarly urged Russian terrorists to focus on attacking Russia in advance of the games, in revenge for Moscow's support of the regime of Syrian President Bashar al-Assad.

Chechen groups are seeking to create a Muslim state in the Caucasus. Terrorists based in the region have often targeted civilians elsewhere in Russia.