The city of Moscow had seen a number of significant attacks in the years prior to the incident . In 2004 , two separate attacks on the Moscow Metro , one by a male suicide bomber on 6 February and another by a female suicide bomber on 31 August ; in 2006 , 13 people were killed in a market bombing ; and in March 2010 , at least 40 people were killed in suicide bombings on the Moscow Metro
suicide bombings on the Moscow Metro
2010 Moscow Metro bombings
Domodedovo International Airport bombing