U.S. President Donald Trump ordered the coordinated airstrikes in response to last weekend's chemical attack that reportedly killed about 70 people in the town of Douma in eastern Ghouta.
Syrian air defences responded to the joint strikes by the United States, France and Britain.
"This collective action sends a clear message that the global community will not stand by and tolerate the use of chemical weapons", May said at a press conference, calling the military action "right and legal".
"It was limited to specific objectives: the destruction of the Syrian regime's chemical capabilities to stop it from committing new chemical massacres". But Syria and Russian Federation have dismissed the reports as fabrications.
There were no details on non-civilian casualties.
Sen. Murray said the she had questions that needed to be answered. A Security Council diplomat said the body would meet later Saturday.
The US president claimed that the joint action was meant to establish a "strong deterrent" against the production, spread, and use of chemical weapons.
"The red line set by France in May 2017 has been crossed", he said.More news: Russia Responds To Syria Air Strikes: "We Are Being Threatened"
More news: Commonwealth Games 2018: Vinesh Phogat wins Gold in Women's 50kg freestyle category
More news: Why Mark Zuckerberg didn't want to talk about your data
Syrian television said the attacks targeted a scientific research centre in Barzeh, near Damascus, and an army depot near Homs while it was reported air defences had hit 13 incoming rockets south of Damascus.
A total of 100 cruise and air-to-surface missiles were launched at targets in Syria, the Russian Defense Ministry stated, noting that two USA warships carried out the attack from the Red Sea, as well as tactical aviation over the Mediterranean Sea and B-1B bombers from al-Tanf area.
Mrs May said chemical weapons had "all too often" been used in recent times.
Trump indicated the strikes would continue until the Syrian regime's use of chemical weapons ends.
"The aggression is a flagrant violation of global law, a breach of the worldwide community's will, and it is doomed to fail", said state news agency SANA.
"The worst apprehensions have come true".
- In response, the Russian embassy in the U.S. said it had warned that such actions would "not be left without consequences", adding that insulting President Vladimir Putin was "unacceptable and inadmissible".
They "are responsible for the regional consequences of this adventurist action", it said, condemning a "clear violation of worldwide rules and laws".