A senior Israeli military official says Syrian President Bashar Assad has used chemical weapons in his battle against insurgent groups trying to topple him.

Brig. Gen. Itai Brun, the head of research and analysis in Israeli military intelligence, told a security conference on Tuesday that Assad has used chemical weapons "in a number of incidents."

He said Syrian forces had probably used sarin, a lethal nerve agent, though he did not provide specifics.

It was the first time Israel has explicitly accused Assad of using chemical weapons, though Britain and France have also said they believe Assad has done so.

Since Syria's civil war erupted more than two years ago, Israel has repeatedly expressed concerns that Assad's chemical weapons could fall into the hands of hostile militant groups.