More Than 300 Chemical Attacks Launched During Syrian Civil War, Study Says

A study released Sunday tallies the chemical weapons attacks over the course of the Syrian civil war. At least 336 have occurred, according to authors Tobias Schneider and Theresa Lütkefend of the Berlin-based Global Public Policy Institute.

That's a number higher than previously known — and "we suspect that the real number may still be significantly higher," they write.

The researchers poured over reports of chemical attacks going back to 2012, reviewing the available information on each to verify the details. They collected evidence from "Syrian and international non-governmental organizations, monitoring groups, private firms, local administrative bodies, relevant international bodies, local and international media, and the open source."

The report's authors attributed 2 percent of the chemical weapons attacks in Syria to the Islamic State.

Syrian President Bashar al-Assad's regime carried out 98 percent of them, according to the authors, dropping chlorine gas, sarin and sulfur mustard gas on Syrian civilians.

"It is clear that the Syrian military has consistently prioritized striking population centers over rebel positions on the frontlines, even in the face of defeat on the ground," they write.