Chemical security

Timeline of Syrian chemical weapon use

Chemical weapons have killed hundreds of people since the start of Syria's civil war, with the U.N. blaming three attacks on the Syrian government and a fourth on the Islamic State group.

Syrian rebels and opposition activists say pro-government forces have used chemical weapons and bombs containing chlorine on numerous occasions. They say a chemical weapons attack on a town in northern Syria on Tuesday killed dozens of people. The Syrian government has denied ever using such weapons.

Here is a timeline of events related to chemical weapons use in Syria.