Chechen insurgents also launched a 2004 hostage-taking raid in the southern Russian town of Beslan, where they took hundreds of hostages. The siege ended in a bloodbath two days later, with more than 330 people, about half of them children, killed.
Insurgents from Chechnya and other regions also have launched a long series of bombings in Moscow and other cities in Russia. An explosion at the international arrivals hall at Moscow's Domodedovo airport in January 2011 killed at least 31 people and wounded more than 140.
Sullivan reported from Washington. Associated Press writer Pat Eaton-Robb contributed to this report from Boston.