![The flag of the President of Russia flies at half mast over the Kremlin as the country observed a day of mourning on Sunday. AP](https://thenational-the-national-prod.cdn.arcpublishing.com/resizer/v2/472AIFJPTRCW7Y3ZJZM5CSB3L4.jpg?smart=true&auth=5b6cd8b02058ac82328720321c850a556878a4db01024f727b647eff44fded1b&width=400&height=225)
The flag of the President of Russia flies at half mast over the Kremlin as the country observed a day of mourning on Sunday. AP
The flag of the President of Russia flies at half mast over the Kremlin as the country observed a day of mourning on Sunday. AP
A brief history of terror attacks against Russia
Attacks in recent years have largely targeted public transport