Attack highlights security challenges

Catalog of deadly assaults in capital

Here is a timeline of major attacks on Moscow in the past two decades.

1999: A bomb blast on Sept 13 at an eight-story apartment building in southeast Moscow kills 118 people. The attack was one of five on apartment buildings that left 293 people dead over a two-week period in Moscow and southern Russia.

2002: A group of 21 male and 19 female Chechen militias storm Moscow's Dubrovka theater on Oct 23 during a musical and take more than 800 people hostage. The standoff with security forces lasts two days and three nights.

It ends when the security forces inject gas into the theater to overpower the attackers and then storm it. A total of 130 hostages are killed.

2003: Two female suicide bombers, identified by Russia as Chechen separatists on July 5, blow themselves up during a rock concert at the Tushino airfield near Moscow, killing 15 people.

2004: A little-known Chechen group detonates a bomb in a packed Moscow subway during rush hour on Feb 6, killing 41 people.

2011: A suicide bomber strikes in the arrivals hall of Moscow Domodedovo International Airport on Jan 24, killing 37 people.

2021: Two female suicide bombers blow themselves up on the Moscow subway on March 29. Forty people are killed.