Moscow holds national day of mourning for victims of terror attack at concert hall, deadliest in 20 years with death toll at least 137. President Putin blames Ukraine while ISIS claims responsibility.
Key Points
Deadliest terror attack in Russia in 20 years
President Putin implicates Ukraine while ISIS claims responsibility
At least 137 people confirmed dead
National day of mourning held in Moscow
Pros
National day of mourning shows solidarity and support for victims' families
Increased awareness and security measures may be implemented to prevent future attacks