Attacks highlight Russian insecurity

A bomb blast tore through a trolleybus in the city of Volgograd on Monday morning on December 30.
A bomb blast tore through a trolleybus in the city of Volgograd on Monday morning on December 30.

    JUST WATCHED

    Attacks highlight Russian insecurity

MUST WATCH

The latest bloodshed in Russia puts focus back on volatile Northern Caucasus. CNN's Matthew Chance reports.