The attacks struck three sites, one in Damascus and two in Homs, which President Donald Trump said were "associated with the chemical weapons capabilities of Syrian dictator Bashar al-Assad."
The action followed a week of threats of reprisals for an alleged chemical weapons attack on civilians in Douma, outside Damascus, where Syrian forces have long been fighting the rebels.
Russian President Vladimir Putin called the missile attacks an "act of aggression against a sovereign state" and said they were against the UN Charter.
Russia, a key ally of the Assad government, calls for an immediate UN Security Council meeting to discuss the "aggressive actions" of the United States and its allies, he said.
Assad said that the air strikes "would only increase the determination of Syria and its people to continue fighting and crushing terrorism in every inch of the country." , "according to Syrian state television.
• Iran's supreme leader, Ayatollah Ali Khamenei, said the United States and its allies had committed a" felony "in Syria.
] • The European Union's foreign policy chief said the EU supported efforts to prevent the use of chemical weapons.
• The UK's Prime Minister, Theresa May, said the action was believed to be Military had been successful.
• Foreign Ministry of Syria The three air strikes were a "flagrant violation of international law".
• Three civilians were injured in Homs after "several" missiles were intercepted by Syrian air defense systems, Syrian state television said.
The Syrian Foreign Ministry urged the international community to "strongly condemn this aggression" and warned that "it would entail an aza for international peace and security as a whole, "in a statement issued by the Syrian Arab News Agency.
Previously, Assad's office tweeted a video of the Syrian president who will go to work on Saturday, with the legend "one morning of firmness".
Danny Makki, a Syrian journalist born in Britain in Damascus, told CNN that strikes roused his neighborhood near the capital. "You could tell right away that this was not an average night battle in Damascus, it was something much bigger," he said.
The Syrians expressed doubts that military action would change anything.
"Frankly I was expecting a stronger attack, especially with the explosions I heard, at least I'm happy that the attacks did not attack civilian areas," said Yasser, 28, a Damascus teacher whose surname was not used by safety reasons.
"I think this attack is a strong message for Assad's chemical weapons, but I do not think Assad is going to change."
Firas Abdullah, a recently evacuated media activist from Ghouta, said: "It's not"
In a televised speech on Friday night announcing the attacks, Trump said he had decided to take action because Assad's action last weekend "was a significant attack on his own people" and "not a man's actions, they are crimes of a monster".
Trump said the purpose of the campaign was "to establish a strong deterrent against the production, spread and use of chemical weapons."
Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff of the United States, told reporters at a Pentagon briefing that the first allied strike was aimed at a scientific research center in greater Damascus involved in the development and production of chemical weapons.
The second site was a chemical weapons storage facility west of Homs, while the third was a storage facility for chemical equipment and an important command post.
Two defense officials told CNN that at least three US ships participated in the airstrikes.
The attacks – the strongest concerted action yet by Western forces in Syria – were launched at 9 p.m. m. ET Friday, as most of Europe and the Middle East was shrouded in darkness.
The Syrian armed forces said in a statement that 110 missiles were fired at Syrian targets and that defense systems of the country "intercepted the majority of missiles, but some reached targets such as the Research Center in Barzeh".
The state news agency TASS reported that none of the missiles fired by the three western nations attacked areas near their naval and air bases in Syria. Those bases are under the protection of Russian air defense units.
A meeting of the North Atlantic Council will be held on Saturday afternoon, a NATO official told CNN. France, the United Kingdom and the United States will inform the allies about the measures taken in Syria, the official said.
May UK: "No on regime change"
In a televised statement on Saturday, May said that British forces had undertaken a "limited and specific strike" and that there was no "viable alternative to the use of the force to degrade "and discourage the use of chemical weapons by the Syrian regime"
While a full assessment has not yet been completed, "we believe the action was successful," he said. "It was not about interfering in a civil war. And it was not a change of regime. "
Although he insisted that the military action was a direct consequence of the alleged attack with chemical weapons in Douma, May also alluded to the use of a nerve agent last month in the English city of Salisbury. "We can not allow the use of chemical weapons to normalize: within Syria, on the streets of the United Kingdom or anywhere else in our world," he said, Britain says that Russia is behind the Salisbury poisoning of a former Russian spy and his daughter, an accusation that Moscow denies.
The French Foreign Minister, Jean-Yves Le Drian, said: "This action is proportional and specific. It does not try to target Assad's allies or the civilian population, but to dissuade the Syrian regime from pursuing its crimes. "
Experts from the international chemical weapons control body, the Organization for the Prohibition of Chemical Weapons, were targeting to the site in Douma before the joint military attacks The group said on Saturday that it would continue to Syria as planned.
The Russian Ministry of Defense said it believed that the action of the Western Allies was not a reprisal for what happened in Douma but was a reaction to the "success" of the Syrian army in liberating rebels' territory.
Iran, another key ally of the Assad government, also condemned the strikes. "I firmly state that the presidents of the United States, France and the British prime minister committed a major crime, "Khamenei tweeted." They will not get any benefit, just as they did not in Iraq, Syria and Afghanistan, in the last years, committing the same criminal acts. "
Syrian state television reported that Assad received a phone call to Saturday from Iranian President Hassan Rouhani in which he said Iran would continue to support Syria.
Turkey, another major actor in the Syrian conflict, said it viewed the air strikes as "an appropriate response" to the Douma Attack.
"We welcome this operation that has alleviated the conscience of humanity in the face of the attack in Douma, suspected in large part by the regime," said the Turkish Foreign Ministry.
German Chancellor Angela Merkel said all available evidence suggested that the Assad regime was responsible for Douma's attack and criticized Russia for blocking an independent investigation through the Security Council.
"The military operation was necessary and appropriate to preserve the effectiveness of the international ban on the use of chemical weapons and to warn the Syrian regime of further violations," Merkel said in a statement expressing support for joint US action. the United Kingdom and France.
"Syria continues to participate and provide a basis for murderous actions, including those of Iran, which endangered its territory, its forces and its leadership," said the Israeli official.
A spokesman for the Jordanian government said that a political solution was the only way to "guarantee the stability, territorial integrity and security of its people." "
The defense minister of Australia issued a statement in support of the strikes, calling them" a calibrated, proportionate and targeted response. "
Mohammed Tawfeeq of CNN, Ryan Browne, Sara Mazloumsaki, Saskya Vandoorne, Frederik Pleitgen, Milena Veselinovic, Nathan Hodge, Tamara Qiblawi and Gul Tuysuz contributed to this report.