"The Syrians initially used industrially produced chemical weapons, but lately they have started to use such substances as chlorine and they use it against civilians. They continue doing it now, during the allegedly holding ceasefire. The are mainly dropping barrels of chlorine from the air," Yaalon said in a speech to a conference near Tel Aviv.
In 2013, a massive chemical weapons attack was carried out in the Syrian suburb of Ghouta which killed more than 1,300 civilians. Both the Syrian government and the militant factions that oppose it blamed one another for the attack.
On February 22, Russia and the United States reached an agreement on a ceasefire in Syria which has been in a state of civil war since 2011. The army loyal to President Bashar Assad is considered to be the only side of the conflict in Syria, which has military aircraft and helicopters.
The truce has been backed by the UN Security Council, which adopted a resolution on Friday, shortly before the ceasefire came into force. The ceasefire is said to be generally holding.