The unnamed woman, who is thought to be part of the same group that struck Moscow's Domodedovo airport on Monday, intended to detonate a suicide belt near Red Square on New Year's Eve in an attack that could have killed hundreds.
Security sources believe a message from her mobile phone operator wishing her a happy new year received just hours before the planned attack triggered her suicide belt, killing her at a safe house.
Islamist terrorists in Russia often use mobile phones as detonators. The bomber's handler, who is usually watching their charge, sends the bomber a text message in order to set off his or her explosive belt at the moment when it is thought they can inflict maximum casualties.
The dead woman has not been identified, but her husband is apparently serving time in jail for being a member of a radical Islamist terror group. More