Brigadier-General Itai Brun made the comments at a Tel Aviv security conference a day after Defense Secretary Chuck Hagel said on a visit to Israel that U.S. intelligence agencies were still assessing whether such weapons had been employed.
President Barack Obama has called the use of chemical weapons a “red line” for the United States that would trigger unspecified U.S. action.
“To the best of our understanding, there was use of lethal chemical weapons. Which chemical weapons? Probably sarin,” Brun said in the most definitive Israeli statement on the issue to date.
Photos of victims showing foam coming out of their mouths and contracted pupils were signs deadly gas had been used, he said.
Forces loyal to Assad were behind the attacks on “armed [rebels] on a number of occasions in the past few months, including the most reported incident on March 19,” Brun said.
The Syrian government and rebels last month accused each other of launching a chemical attack near the northern city of Aleppo.
On Monday, Hagel said the use of chemical weapons by Assad’s forces would be a “game changer” and the United States and Israel “have options for all contingencies.”
Discussions between Syria and the United Nations on a U.N. investigation of possible use of chemical weapons have been at an impasse due to the Syrian government’s refusal to let the inspectors visit anywhere but Aleppo, diplomats and U.N. officials said last week.
U.N. diplomats said Britain and France provided Ban’s office with what they believed to be strong evidence that chemical weapons also were used in Homs.
Brun, who was speaking at the annual security conference of The Institute for National Security Studies at TAU, said Israel’s military was studying a number of future scenarios facing Syria.
“More likely, as time goes by, are the scenarios of chaos and anarchy, or that of [Syria] breaking up into cantons. These pose major challenges for Israel.”