- Syrian Foreign Ministry delivers letter to U.N. complaining of ISIS atrocities in al-Bagaliyeh
- Human rights group estimates at least 400 civilians have been abducted and killed
- Deir Ezzor is a strategic gateway to Iraq and is surrounded by ISIS-controlled oil fields
(CNN)The city of Deir Ezzor in northern Syria has seen more than its share of conflict and suffering since the Syrian insurgency began. But the last few days have seen unprecedented horror, including suicide bombings, mass abductions and arbitrary killings, according to human rights activists.