The United States, Britain and France launched air strikes on Syria on Saturday, targeting sites associated with the Middle Eastern country's chemical weapons capabilities.
U.S. President Donald Trump said the combined operation of "precision strikes" against Syrian President Bashar al-Assad's government was in response to its alleged use of chemical weapons on its citizens near Damascus.
"We're prepared to sustain this response until the Syrian regime stops its use of prohibited chemical agents," Trump said Friday in a televised address from the White House.
The defense ministry of Russia, which has been backing Assad's government in Syria's civil war, said no one was killed in the strikes.
It is the second U.S. military action to be carried out against the Assad government since April last year when the United States conducted a missile strike on an air base thought to be the origin of another alleged chemical attack on civilians.
Speaking after the strikes, both Trump and British Prime Minister Theresa May took aim at Russia for enabling the use of chemical weapons in Syria.
Russian President Vladimir Putin, meanwhile, criticized the strikes as "an act of aggression against a sovereign state," in violation of international law.
In a statement, he said Russia has been "assisting the legitimate government in its counterterrorism efforts" in Syria and will convene an emergency meeting of the U.N. Security Council to discuss the "aggressive actions" of the United States and its allies.
The targets of the strikes, some carried out with U.S. Tomahawk cruise missiles, were military bases and chemical research facilities around Damascus and near the city of Homs further north.
In the Syrian capital, explosions were heard and flashes of light were observed at around 4 a.m. local time.
Reuters news agency quoted a Syrian government official as saying Russia had provided advance warning of the strikes, allowing it to evacuate targeted bases several days ago.
The British government described the strikes as successful, with May saying the military action was "both right and legal."
At a press conference at her office, May said the action was not aimed at regime change, but was a necessary response to a chemical attack a week earlier on a rebel-held town near Damascus.
"We have no choice but to conclude that diplomatic action on its own will not be any more effective in the future than it has been in the past," she said.
French President Emmanuel Macron said in a press statement that the operation "has been limited to the Syrian regime's facilities enabling the production and employment of chemical weapons."
"We cannot tolerate the normalization of the employment of chemical weapons, which is an immediate danger to the Syrian people and to our collective security," Macron said.
The state-run Syria Arab News Agency quoted foreign ministry officials as saying the strikes were intended to impede an investigation by the Organization for the Prohibition of Chemical Weapons into the alleged chemical attack, scheduled to start on Saturday.
In Moscow, Russian media cited a defense ministry statement saying the strikes involved more than 100 missiles, most of which were intercepted by Syrian missile defense systems, and Russia did not use its own defense systems deployed in Syria.
Anatoly Antonov, Russia's ambassador to the United States, warned in a Facebook post that "such actions will not be left without consequences."
The strikes followed heated debate on Syria and chemical weapons at the U.N. Security Council.
China -- the other permanent Security Council member alongside Russia and the three allies that launched the strikes -- said it opposes any use of force and believes unilateral military action will "further complicate the Syrian issue."
"China urges the relevant parties to return to the framework of international law and resolve the issue through dialogue and negotiation," a Foreign Ministry spokeswoman said.
U.N. Secretary General Antonio Guterres called on all member states to "show restraint in these dangerous circumstances and to avoid any acts that could escalate the situation and worsen the suffering of the Syrian people."
Iran condemned the strikes, while U.S. allies like Japan, Australia and Israel voiced support.