The Pentagon said the strikes, which began at 4am Syrian time (9pm EST), involved planes and ship-launched missiles and destroyed three targets: a chemical weapons storage facility west of Homs, another storage site and command post nearby, and a scientific research center in Damascus.
The drone attack on Israel was "the first time we saw Iran do something against Israel, not by proxy".
The media reports were contrasted with denials of the attack by supporters of the Syrian government.
Israeli officials have repeatedly said they will act to prevent Iran's growing military presence in Syria and the region remains on edge after US-led air strikes targeting the Syrian regime were unleashed in the early hours of Saturday.
On Saturday, the UN Security Council rejected a resolution put forward by Russian Federation condemning the strikes by the US, Britain, and France. For them, Syria is less important than US President Donald Trump's decision on the Iranian nuclear deal, due in less than a month, on May 12.More news: Kenya election officials quit, pressure on chairman to go
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But the President hoped it would be enough to deter Assad from using chemical weapons again without being so damaging as to compel Russian Federation and Iran to intervene.
Speaking via satellite link to his supporters in Beirut Friday, Nasrallah called the alleged chemical weapons attack in Douma "theater". "The United States, France and Britain proved their commitment to fight chemical warfare is not limited to just declarations".
"These are not the actions of a man", Trump said of last weekend's attack in a televised address from the White House Diplomatic Room.
Israel, which was not involved in Saturday's unprecedented wave of missile strikes but expressed full support, has unilaterally launched air raids on targets inside Syria on several occasions.
In a televised speech from the White House, Trump said "To Iran, and to Russian Federation, I ask: What kind of a nation wants to be associated with the mass murder of innocent men, women and children?" It fears Iran could use Syrian territory to stage attacks or form a land corridor from Iran to Lebanon that could allow it to transfer weapons more easily to Hezbollah.