Syrian President Bashar al-Assad has used chemical weapons against the armed rebels attempting to oust him from power, a senior Israel military officer said on Tuesday.

“In our estimate, the (Syrian) regime has used, and is using, chemical weapons,” said Brigadier Itai Brun, the head of the Israeli military’s intelligence research division.

Pictures taken of victims with contracted pupils and foaming mouths indicate deadly nerve gas — “probably sarin” — had been used by regime forces, said Brig. Braun at a conference held at Tel Aviv University.

“These are troubling developments,” he said. “The use of chemical weapons, without an adequate response from the world, could signal that this is legitimate.” “We should be very worried by the possibility that chemical weapons could fall into irresponsible hands who do not act according to gain-loss considerations,” he went on.

Israel has repeatedly expressed concern that Syria’s large chemical weapons arsenal — estimated as being more than 1,000 metric tonnes — would fall into the hands of Islamic militants.

According to foreign reports, Israeli jets in January targeted a convoy of weapons in Syria believed to be destined for Hezbollah militants in Lebanon.

Defence Minister Moshe Ya’alon said on Monday that Israel was “ready to act” if chemical weapons were transferred to hostile groups. Both U.S. President Barack Obama and his Defence chief Chuck Hagel, who is in the region, have said use of such weapons would be a “game changer.” Britain and France have also said there is credible evidence that chemical weapons have been used recently in Syria. The UN said last month that it would send a fact-finding mission to the country to investigate the allegations.

NATO concerned

Meanwhile, the NATO military alliance is “extremely concerned” about the possible use of chemical weapons in Syria, its chief said in Brussels on Tuesday, refusing to comment specifically on Israeli allegations that the arms have already been used against rebels.

NATO Secretary General Anders Fogh Rasmussen listed chemical weapons, the humanitarian situation, and the risk of a regional spill over among the main concerns for the alliance.

“There is no call for NATO to play a role, but if these challenges remain unaddressed, they could directly affect our own security,” Mr. Rasmussen told journalists in Brussels. “So we will continue to remain extremely vigilant.”

He refused to comment on contingency plans that the alliance may have in case chemical weapons are used in Syria. He said NATO had “all plans in place to ensure the effective defence and protection of Turkey,” which neighbours Syria and is a NATO member.

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